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Daan van den Broek @daanvandenbroek.com · 01/10/2026

Despite some loud thunder last night, and a few showers this morning, the situation in Malia is relatively calm so far.⚡️ Emergency notifications are coming from different directions this morning, however.

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Daan van den Broek @daanvandenbroek.com · 01/10/2026

Extreme weather in Crete. 🇬🇷 Torrential rains, regionally >100 mm in 2 hours. 🌧️ ⚠️ risk for flash floods, land- and mudslides, esp. in mountainous terrain. Code red is issued, and emergency notifications were sent out this morning for certain areas. 🚨

Precipitation sums today, so far (in mm) around Greece. Source: https://www.meteo.gr/crete/index.cfm?

Emergency warnings that appeared on phones this morning.

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

📚 Paper alert! Our paper "The 2026 cold wave brought northern Fennoscandia its coldest two-week period since 1987" is out now in Weather. 🧵(1/14)

(a) ERA5 2m temperature anomaly between 31 December 2025 and 13 January 2026, with the analysis domain (66°N–69°N, 20°E–30°E)indicated in red. (b) ERA5- based time series of the lowest 14-day mean temperature over the northern Fennoscandia analysis domain highlighted in (a) (land-only). Winter 2025/2026 is circled in red.

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Mika Rantanen @mikarantane.bsky.social · 25/09/2026

New paper by @daanvandenbroek.com and me just published in @rmets.org Weather: "The 2026 cold wave brought northern Fennoscandia its coldest 2-week period since 1987" rmets.onlinelibrary.wiley.com/doi/10.1002/... Check out the brilliant thread by Daan below 👇

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

For more information and details, read the complete article in Weather! 📄👇 🔗 doi.org/10.1002/wea.... 🧵End (14/14)

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

Finally, after 13 January, warm air advection from the south and increased mixing destroyed the inversion, warming the lower atmosphere again and marking the end of the cold wave. This event nicely demonstrated that extreme and persistent cold remains possible in a warming climate. 🧵(13/14)

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

Calm, clear-sky conditions under the high pressure system favored strong radiative cooling of the Earth's surface. Consequently, (near-)surface temperatures decoupled from warmer air above. The surface inversion strength in Sodankylä reached up to 30°C, as T2m reached low -30s and regionally -40s.

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

The cold wave was initiated by strong cold-air advection from the north during the preceding week. The cold then intensified beneath a high-pressure system centred over northern Fennoscandia. 🧵(11/14)

Weekly mean 500hPa geopotential height (m; shading) and 300hPa wind speed (ms−1; white contours at 10ms−1 intervals starting from 20ms−1).(d–f) Weekly mean 850hPa temperature (°C; shading) and mean sea-level pressure (hPa; black contours) for the week preceding the cold wave (a,d), week 1 ofthe cold wave (b,e), and week 2 of the cold wave (c,f).

Same as the previous figure, but with values represented as anomalies against the 1991-2020 climatological baseline.

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

We note that the minimum temperature measured during this event is −42.8°C on 9 January. Extremely cold, but nowhere near a record low. This shows that the defining characteristic of this cold wave lies in the persistence of the extreme cold, not in individual minimum temperatures. 🧵(10/14)

The lowest temperature measured in Finland for every winter from 1959-2026. With a minimum temperature of -42.8°C, it got very cold, but still very far from Finland's all-time records. Figure by Mika Rantanen.

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

- Savukoski Kirkonkylä and Sodankylä Lokka weather stations saw their coldest 14-day period since 1966. - Ylitornio Meltosjärvi was the most extreme: it measured the coldest 14-day period in its measurement history at -29.8°C, making it the coldest since at least 1964! 👇 🧵(9/14)

Time series of the lowest 14-day mean temperature in each winter (labelled by ending year) at Ylitornio Meltosjärvi, Finland.

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

Luckily, stations with shorter measurement series exist near this area, and those confirm that regionally, the cold was even more extreme. 👇 🧵(8/14)

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

But: ERA5 spatial rankings show that the 2026 cold wave was among the most extreme in the dataset across a broad area of northern Fennoscandia. And the highest-ranked grid cells lie away from the long-term stations, suggesting those stations underestimate the regional severity of the cold.

Spatial ranking of the 2025/2026 coldest 14-day mean temperature, expressed as the rank of that winter relative toall winters in the ERA5 dataset (1941–present), with rank 1 indicating the coldest on record. A widespread area from the southern Finnish-Swedish borderregion into Northern Finland was ranked as the second coldest 14-day period in the ERA5 dataset

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

Sodankylä, 🇫🇮: coldest 14-day period since 1999 - together with that year, the coldest since 1987. Karesuando, 🇸🇪: coldest since 1980 (4th coldest in the full observational record -since 1879- at −31.8°C).🥶 Karasjok, 🇳🇴: less extreme as only the second coldest 14-day period this century, after 2014.

(a–c) Time series of the lowest 14-day mean temperature in each winter (labelled by ending year) at the (a) Sodankylä Tähtelä, (b) Karesuandoand (c) Karasjok weather stations. (d) Spatial ranking of the 2025/2026 coldest 14-day mean temperature, expressed as the rank of that winter relative toall winters in the ERA5 dataset (1941–present), with rank 1 indicating the coldest on record. A widespread area from the southern Finnish-Swedish borderregion into Northern Finland was ranked as the second coldest 14-day period in the ERA5 dataset. The locations of the three observational stations shownin panels (a–c) are indicated in panel (d), and in addition, the weather station Ylitornio Meltosjärvi, with a shorter time series, is indicated by a red cross.

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

Temperature anomalies in this region reveal that the cold was most extreme in the border region between Finland and Sweden, with anomalies locally peaking below -18°C compared to the 1991-2020 average. Next, we analysed other long term weather stations in the region. 👇 🧵(5/14)

(a) ERA5 2m temperature anomaly between 31 December 2025 and 13 January 2026, with the analysis domain (66°N–69°N, 20°E–30°E)indicated in red.

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

We continued by looking at a regional perspective, based on ERA5 data. Here we found that the area averaged temperature over Northern Fennoscandia was the coldest since 1987, at -25.2°C. 🧵(4/14)

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

We started by analysing Sodankylä weather station, the longest temperature time series in Northern Finland. At this station, the 14-day period between 31 Dec 2025 and 13 Jan 2026 was extremely cold, with 13 days below the 10th percentile of daily mean temperatures and a mean temp of -28.8°C.

(a) Daily average and (b) daily minimum temperature for the Dec 2025–Jan 2026 period at Sodankylä Tähtelä in situ observation station.Colours show daily temperature with respect to the 1991–2020 median. The grey background shading displays the 10th–90th percentile range calcu-lated from the 1991–2020 climatology, and the grey lines indicate all-time maximum and minimum observations from the full 1908–2025 record. The2026 cold wave is highlighted with hatching. The median and 10th–90th percentile lines have been smoothed with a Gaussian filter.

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

Large areas of Lapland experienced their coldest two-week period since 1987. Regionally, those two weeks were even the coldest since at least 1964. 🥶 This work was carried out together with @mikarantane.bsky.social. 🔗 Read the full paper here: doi.org/10.1002/wea.... 🧵(2/14)

doi.org

The 2026 cold wave brought northern Fennoscandia its coldest 2‐week period since 1987

During late December 2025 and January 2026, a severe and long-lasting cold wave affected northern Fennoscandia. In this article, we aim to quantify the extremity of the 2026 cold wave and evaluate…

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Daan van den Broek @daanvandenbroek.com · 25/09/2026

📚 Paper alert! Our paper "The 2026 cold wave brought northern Fennoscandia its coldest two-week period since 1987" is out now in Weather. 🧵(1/14)

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Daan van den Broek @daanvandenbroek.com · 24/09/2026

A strong southerly flow will estabilish between a deep trough over the Atlantic and a strong high pressure system over northern Europe, advecting very warm air. Sunny conditions under the high pressure system will add to the summer-like feeling. ☀️

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Daan van den Broek @daanvandenbroek.com · 24/09/2026

🌡️ ☀️ Exceptional warmth seems imminent late September and early October for western and northern Europe. Temperature anomalies of +10-+16°C are possible at 850 hPa (~1400 m altitude).

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Daan van den Broek @daanvandenbroek.com · 10/09/2026

The purple pixel was responsible.

Radar image of Helsinki. The purple pixels indicate very heavy precipitation.

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Daan van den Broek @daanvandenbroek.com · 10/09/2026

Very heavy rainfall in northern Helsinki. The playground started to flood.

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Daan van den Broek @daanvandenbroek.com · 09/09/2026

First year with a garden plot in northern Helsinki, and our pumpkin experiment certainly turned out successful. 🎃 Harvested on Sunday, before the weather turned too cold. Guesses for the weight?👇🏼

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Daan van den Broek @daanvandenbroek.com · 02/09/2026

🌡️ Unsurprisingly, the Netherlands measured it's warmest summer on record, at an average temperature of 19.3°C. 2018 is now the 2nd warmest at 18.9°C. 8 out of the 10 warmest summers on record took place since 2003.

Summer temperatures at De Bilt, in the Netherlands, with the summer of 2026 marked by a red circle. The summer 2026 was the warmest on record at 19.3°C. Black line indicates the trend between 1980 and 2026.

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Daan van den Broek @daanvandenbroek.com · 02/09/2026

At 36.8°C, de Bilt also measured its second highest annual maximum temperature. The record for the Bilt remains at 37.5°C, measured in 2019 - when southern and eastern parts of the Netherlands measured well over 40°C.

The annual maximum temperature in the Netherlands. 2026 measured the 2nd highest annual temperature, behind 2018.

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Daan van den Broek @daanvandenbroek.com · 02/09/2026

This summer measured 11 'tropical days' (Tx ≥ 30°C), 2 days short of the record from 1947 and 1976 (13). Interestingly, if we set the bar at 33°C, the summer of 2026 annihilated any other year.

The number of 'tropical days' (maximum temperature equal to or greater than 30°C) during each summer since 1901 in the Netherlands. The summer of 2026 is marked by a red circle, the black line indicates the trend since 1901.

The number of days with a maximum temperature equal to or above 33°C. 2026 is marked in red.

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Daan van den Broek @daanvandenbroek.com · 02/09/2026

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Daan van den Broek @daanvandenbroek.com · 25/08/2026

Last weekend's storm in the Baltics regionally dumped >100mm precipitation. According to @edhawkins.org, climate warming caused 15-20% more precipitation than would have been the case without warming.

Last weekend's storm in the Baltic States left regionally 15-20% more precipitation than would have been the case without climate warming.

Figure shows a model run of the actual weather situation (left), a model in the cooler climate of 1950 (central panel) and the difference between the two (right), where green colors indicate more precipitation.

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Daan van den Broek @daanvandenbroek.com · 25/08/2026

A global record high sea surface temperature is not just the consequence of a record-breaking El Niño. It's the fact that this record-breaking El Niño compounds on top of decades on top of human-driven warming

The sea surface temperature anomaly. Large parts of the world's oceans are extremely warm, and the El Niño signature is clearly visible.

Anomalies are relative to 1991-2020, an already warmed baseline.

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Daan van den Broek @daanvandenbroek.com · 25/08/2026

According to Copernicus, the global average sea surface temerature has reached its highest value since the start of the measurements. 🌡️ On 22 August global mean sea surface temeratures reached 21.10°C, exceeding the previous record of 21.09°C.

Daily mean sea surface temperature between 60S and 60N, measured between 1979 and 2026. Th current 2026 value is, the largest on record. Source: Copernicus/ECMWF

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Daan van den Broek @daanvandenbroek.com · 23/08/2026

While winter storms tend to be more extreme than summer storms, the latter can still be more damaging because trees are still in full leaf, causing stronger wind loading. In addition, the heavy rain softened the ground before the strongest gusts arrived.

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Daan van den Broek @daanvandenbroek.com · 23/08/2026

🇱🇻 Various sources reported Latvia’s most destructive storm since January 2005. ⚡ ~160,000 customers without power at 21:00 🌳 Widespread fallen trees, blocked roads 🚆 Rail disruption 🌧️ Around half a month’s rain in one day (locally >100 mm)

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Daan van den Broek @daanvandenbroek.com · 22/08/2026

The dark nights are returning to Helsinki. 🌌 Tonight, for the first time in four months, the Sun dips more than 18° below the horizon. Instead of astronomical twilight, the darkest part of the night will be fully dark again. Only ~45 minutes tonight, but increasing from here. Autumn is coming.

Sunrise, sunset and twilight table for Helsinki in August 2026. Red boxes highlight 22 August and the astronomical-twilight column: astronomical twilight still lasts throughout the night on 22 August, while full darkness returns on 23 August, from 00:50 to 01:56. Source: timeanddate.com (https://www.timeanddate.com/sun/finland/helsinki)

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Daan van den Broek @daanvandenbroek.com · 21/08/2026

The rain starts around Saturday morning in Lithuania and Latvia, afternoon in Estonia and evening in southern Finland. The majority of the rain falls until Sunday morning/afternoon, after which the low pressure system moves away eastward.

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Daan van den Broek @daanvandenbroek.com · 21/08/2026

The precipitation is related to a rapidly deepening low-pressure system, developing along a sharp baroclinic zone under a strong jet stream. In addition, a lot of moisture is drawn northwards from the Mediterranean towards the Baltic states and Finland. 👇

Forecast map of total-column water vapour (TCWV) over Europe. A long, narrow plume of moist air (atmospheric river-like) extends northwards from the Mediterranean and central Europe across the Baltic states into Finland and northwestern Russia.

TCWV locally up to 40-50 mm over the Baltic States, exceptionally high for this region.

Source: ECMWF

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Daan van den Broek @daanvandenbroek.com · 21/08/2026

A potentially significant rainfall event deserves attention from Saturday through Sunday evening across the Baltic states and southern and eastern Finland. 🌧️ 🇫🇮 Regionally 30–50 mm 🇪🇪🇱🇻🇱🇹 Local totals could exceed 100 mm ⚠️ strong winds are possible too!

Accumulated precipitation until Monday 3 am local time, as projected by the FMI MEPS model. A lot of precipitation is forecast over parts of the Baltics and southern and eastern Finland. The brighter the colors, the higher the total precipitation. The numbers indicated projected accumulated precipitation in mm.

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Daan van den Broek @daanvandenbroek.com · 19/08/2026

The North Sea off the Dutch coast has just set a new temperature record. 🌊 🌡️ At Lichteiland Goeree, daily mean seawater reached 21.5°C on 15–17 August, the highest since measurements began in 1984. The current marine heatwave has now lasted 80+ days.

North Sea water temperature measured at Lichteiland Goeree, measurements starting in 1984. The black line, indicating 2026, shows the warmest year on record.

Source: KNMI

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KNMI @knmi.nl · 19/08/2026

Afgelopen weekend steeg de temperatuur van de Noordzee voor de kust van Nederland uit boven alle eerdere metingen. Bij Lichteiland Goeree, 30 kilometer uit de kust bij Hoek van Holland steeg de etmaalgemiddelde zeetemperatuur tot 21,5 graden, de hoogste waarde sinds het begin van de metingen in...

knmi.nl

Noordzee was niet eerder zo warm

Afgelopen weekend steeg de temperatuur van de Noordzee voor de kust van Nederland uit boven alle eerdere metingen. Bij Lichteiland Goeree, 30 kilom...

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Daan van den Broek @daanvandenbroek.com · 19/08/2026

More👇🏼 bsky.app/profile/knmi...

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Daan van den Broek @daanvandenbroek.com · 19/08/2026

As a consequence of climate change, sea water at this location has warmed ~0.4°C per decade since 1984. ☀️On top of that warming baseline, this summer’s calm weather (high pressure), sunshine, and exceptional heat did the rest.

Daily temperatures at Lichteiland Goeree, with long term trends indicated by the lines. Source: KNMI

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Daan van den Broek @daanvandenbroek.com · 19/08/2026

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Daan van den Broek @daanvandenbroek.com · 19/08/2026

Source: eu-space.europa.eu/components/e...

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Daan van den Broek @daanvandenbroek.com · 19/08/2026

The worst of Europe’s extreme atmospheric heat is gone, but it certainly left a signature in the ocean. A new attribution study finds: - the current event in the Mediterranean ~2°C warmer due to antropogenic global warming. - seas off western Europe 1.3–1.4°C than without AGW.

Data visualisation of sea surface temperature anomalies from Copernicus, based on Copernicus Marine Service data for 13 August 2026. (dark) red tones indicate areas where sea surface temperatures were above the long-term average. The largest anomalies, reaching approximately 6°C above average, were recorded in the western Mediterranean Sea, particularly in the Gulf of Lion off the coast of southern France. Values above 5°C were also recorded in the Atlantic off the Iberian Peninsula. Cooler-than-average waters are visible in parts of the Aegean Sea. Source: eu-space.europa.eu.

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Daan van den Broek @daanvandenbroek.com · 18/08/2026

Beautiful rain during sunshine at Suomenlinna yesterday evening.

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Daan van den Broek @daanvandenbroek.com · 18/08/2026

It seems like the Rhine at Lobith reached the record minimum daily discharge yesterday August 17th, at 565 m³/s. With today's rainfall in the catchment area, discharge started to rise. More much-needed rain in upcoming days!

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Daan van den Broek @daanvandenbroek.com · 17/08/2026

📉 The Rhine’s discharge keeps falling: one week after reaching a record low, it has now dropped below 600 m³/s for the first time on record. 🌧️ Fortunately, the much needed rain is finally returning to the Rhine basin and the Alps, so discharge should rise again soon. 🧵 (1/3)

Graph showing the daily Rhine discharge at Lobith from June to December. In 2026 (red line), discharge fell to 569 cubic metres per second on 16 August, below the previous record of 620 in November 1947 (blue line).

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Daan van den Broek @daanvandenbroek.com · 17/08/2026

🌧️ Fortunately, much-needed rain is finally coming to western and central Europe, including the Alps and much of the Rhine catchment. This should allow the Rhine’s discharge (and that of other rivers in Europe) to start recovering soon. 🧵(3/3)

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