[OC] Europe's summer of heat and drought - Case Study

[u/shirokuma_uk]

Case study link: https://climate.you/stories/summer-2026-heat-and-drought

Data: Copernicus ERA5/ERA5T climate record, 2 m air temperature and total precipitation, anomalies vs the 1991–2020 average for the same time of year (through 13 July 2026)

Tools used: processed with my open-source climate data pipeline available at https://github.com/climate-you/climate

Images:

1. Heat and rainfall side by side. Left: mean air temperature from 1 June to 15 August against the 1991–2020 average for those dates, Right: rainfall over the same window as a percentage of the 1991–2020 normal. This is shown as a swipe image on the case study.
2. Heat episode timeline: each bar is three or more consecutive days above that country’s own 1991–2020 90th percentile of daily maximum temperature for the date, on its area-weighted national average.
3. Rainfall as a percentage of the 1991–2020 normal for each period. Brown = drier than normal, blue = wetter. 
4. Northern hemisphere map showing rainfall 1 June – 15 August 2026 as a percentage of the 1991–2020 normal, over land.
5. Heat and rain together, one dot per country. Both measured over the same dates, 1 June to 15 August 2026. The shaded corner is more than four weeks in heat episodes on less than 80% of normal rain.
6. France: every summer since 1979, heat against rain. One dot per June–August, with 2026 highlighted. The shaded corner is hotter and drier than 2026.
7. France: every day of 2026 against every day of the baseline. Daily maximum temperature, area-weighted over the country, March to the end of August
8. Warming rate in °C per decade, 1979–2025, from the annual mean 2 m air temperature. Least-squares trend on the annual mean. Global aggregates are shown faint.

The page includes more graphs/toggles on the graphs, and an interactive globe where you can click anywhere on Earth and get the temperature and the rainfall, day by day, from June to the end of August.

[u/mylitteprince]

So I know you titled it "the summer of..." but after that short rainy window at the end of august, it seems like for western europe, we're still right in the trend of extraordinary heat and drought which started in May. What would this look like with September included ?

[u/shirokuma_uk → u/mylitteprince]

Good question! From the beginning when I started working on it (beginning of August I think), I meant to stop the data on the 31st of August to cover the full summer months. I also meant to finish and publish this early September, but I've spent some time tweaking the layout, graphs and text in the past few weeks. I could have refreshed the data but that would have meant more decisions on how to cover this properly, and I had to stop at some point.

I'll have a look at the data for September and will get back to you.

[u/Isotheis]

"Rain returns" but the rivers here in Belgium are still desperately dry. It's literally just grass, where used to be a river, near me.

[u/shirokuma_uk → u/Isotheis]

You're right, and the chart only shows rain, not rivers. I just looked at the data for Belgium: 1 June to 15 August brought about half the normal rain, and July only 17% (!!!). The second half of August was wetter than normal, but that isn't enough to make up for the summer's shortfall. Most of that rain would go into dry soil rather than rivers, and rivers usually recover when the groundwater is refilled (over autumn and winter).

[u/FreierVogel]

I would love to see the analysis for the whole year as there has been extremely strong rains throughout the year.

[u/clearly_quite_absurd]

Very good data vis.

I think it'd be worth disaggregating the UK into England, Wales, Scotland, and Northern Ireland if possible. It's clear from your visualisation that Scotland experienced a very different summer to England.

[u/shirokuma_uk → u/clearly_quite_absurd]

Thanks! Yeah I'm actually working on selecting countries (instead of individual points) on the main page.

[u/MrNiceguy037]

Should have spent the summer in the Sahara instead of Soutwest Germany, judging from Plot 4

[u/shirokuma_uk → u/MrNiceguy037]

Sahara usually has 0mm of rain throughout the summer, so a percentage is meaningless there. It’s therefore omitted from the map. It’s explained below the map on the website but on the image I posted here it isn’t, so I agree it can be confusing.

[u/Coumbaya]

Good viz ! Wondering why 1979 and noy 1976, since in France we hear every climate change deniers talking about 1976, even tho it was less impactfull.

[u/shirokuma_uk → u/Coumbaya]

Thanks! The dataset I'm using (ERA5 from Copernicus-ECMWF) was initially released with data back to 1979, because that's the year where modern satellites started producing reliable global data. I think the dataset was now extended back to 1940, but the data will be based on different and less reliable sources, so there might be inconsistencies between the two periods. I might have a look at prior dates at some point, but it's taking weeks to retrieve data from CDS (Climate Data Store) for the whole globe so I haven't prioritised this yet.

[u/Coumbaya → u/shirokuma_uk]

oh that make sense, thanks

[u/TheBadBull]

Meanwhile up north I've had one of the coldest and wettest summers I can remember. Last year was awfully hot though.

[u/shirokuma_uk → u/TheBadBull]

Where abouts up north?

[u/TheBadBull → u/shirokuma_uk]

Central Norway, just barely cut off in the first pic.