The June 2026 heatwave, seen from space

Each pixel covers 100 m × 100 m. The dark red is roofs, car parks and business parks; the sea green, forests and valleys. Esch and the southern belt stand out at once — but pockets of heat also appear in Remich, Grevenmacher and around the airport.

1 July · harmonised +6.3 °C 24 June · peak of the heatwave

Surface temperature

24 °C3848≥ 62 °C

À gauche du liseré pointillé : passage du 1ᵉʳ juillet (le 24 juin, le satellite ne survolait pas cet angle), affiché harmonisé de +6,3 °C — l’écart médian mesuré sur 4,2 millions de pixels de recouvrement. Les taches claires sont ses nuages, masqués. Aucun classement ne mélange les deux dates.

This is ground temperature, not air temperature: ground at 50 °C coexists with much lower air. It is the heat that surfaces store, then partly release back at night.

Across the 1,602 km² observed on 24 June — 62 % of the territory, the north-west not having been overflown that day — the surface splits between a cool mode around 34-36 °C (forests, farmland, valleys) and a broad shoulder above 40 °C (roofs, roads, business parks); the median falls between the two, at 38.7 °C. 39 % of that observed surface exceeded 40 °C, 0.9 % exceeded 50 °C. Set against the whole country the figure would be lower: the missing part is the coolest.

Distribution of the national surface by temperature, 24 June pass (30 m grid, ~100 m native information). The line marks the 40 °C threshold; the median is indicated.

Read at commune scale: a commune’s population is set against the hot share of its territory, without pinpointing residents within it. Base: the 72 communes observed on 24 June, i.e. 550,817 residents; the other 28 (143,090 residents) were not seen during the peak.

Same day, same hour: the 95th percentile of surface temperature runs from 53.4 °C in Esch-sur-Alzette to 40.4 °C in Larochette — a 13 °C gap that reflects geography, building density and vegetation. Pick an indicator:

† Western-band communes: measured on the 1 July pass (episode over, −6.3 °C measured gap) — their thermal values are not comparable with those of 24 June and are not ranked with them. The table keeps their raw values; only the map and the choropleth show the harmonised version. The share of over-65s (population register) does not depend on the date. ° 24 June communes where more than a quarter of the territory was only seen on 1 July: partial coverage, statistics to be read with caution.

A communal average hides a lot: for an adaptation policy, what matters is the gap between a commune’s built core and its cool spaces. This intra-commune thermal range — the 95th percentile minus the 25th — reaches 17.1 °C in Esch-sur-Alzette: the commune holds both very hot islands and cool pockets, and therefore room for manoeuvre. A small range does not mean a cool territory: Frisange shows only 6.1 °C of range, but 72.7 % of its ground exceeded 40 °C — hot almost everywhere, and so without a cool reserve nearby.

The 15 communes with the largest internal range (24 June). The bar runs from the 25th percentile (cool zones) to the 95th (built core) of each commune. This is not an urban heat island index in the strict sense: there is no rural reference, and the result depends on communal boundaries.

A hot, young commune does not have the same problem as a hot, ageing one. The top-right quadrant — hotter and older than the median of the 72 communes observed on 24 June — concentrates the health risk: it includes Mondorf-les-Bains, Remich and Niederanven, where more than one resident in five is 65 or over. Circle size shows the number of residents aged 65 and over.

Aggregated by canton — and only over the communes seen on 24 June — the gaps narrow: from 49.8 °C in the Esch-sur-Alzette canton to 41.6 °C in the Vianden one. Four north-western cantons are too sparsely covered that day to be compared: their absence is precisely what rules out concluding a “north-south gradient”, since the coolest part of the country was not observed during the peak.

Type a commune’s name to see its card: surface heat, internal contrast, share of older residents, and its position in the 24 June ranking.

The heat mapped here is not an isolated phenomenon. As these lines were finalised (28 July 2026), a fire that broke out at Saumos, west of Bordeaux, on 22 July had burned through some 42,000 hectares according to the Gironde prefecture; more than 220,000 people had been evacuated across 24 communes, the Cap Ferret peninsula partly by sea. The fire was “stabilised”, not yet contained. On its own, it is twice the size of Gironde’s historic July 2022 fires (La Teste-de-Buch and Landiras, roughly 21,000 ha combined).

Three reference points, drawn from official tallies and open data, all dated:

• France. Nearly 98,000 ha burned since 1 January as of 25 July (Interior Ministry), around 116,000 by 27 July (presidential statement); 2022, the previous benchmark year, closed at roughly 72,000 ha. The satellite confirms the anomaly: by 22 July, EFFIS was already measuring the highest year-to-date total at this point of the year in twenty years of records. The Gironde fire has also generated pyrocumulonimbus, fire-born storms never before documented in France.
• Europe. 254,388 ha burned in the EU by 22 July across 1,254 detected fires (JRC/EFFIS), more than double the 2006-2025 average for that date; Spain (around 140,000 ha), Italy and France are the hardest hit. Copernicus also measured Western Europe’s warmest June on record (+3.1 °C above the 1991-2020 norm): the heatwave analysed on this page was part of it.
• Luxembourg. No mega-fires here, and that is no accident: fragmented woodland (about 35% of the territory), mostly broadleaf, a still-temperate climate. In 2025, Europe’s record year (more than one million hectares burned in the EU), Luxembourg and Malta were the only two member states without a single fire mapped by EFFIS. But the risk is rising: the CGDIS counted 35 vegetation fires in the 15 days before 20 July (5 ha burned at Greiveldange on the 18th, a field fire that spread into woodland at Consdorf on the 12th); hot summers exceed 200 call-outs, against about thirty in a cool one. In late July, MeteoLux had the country on yellow heat alert (36 °C expected on the 29th), and the national drinking-water vigilance phase had been running since 10 July.

Figures as of 28 July 2026; an active fire outdates them within hours. EFFIS totals are rapid satellite estimates (fires of roughly 30 ha and above), continuously revised, and differ from national tallies. One reminder: the surface temperature mapped here measures heat exposure, not directly wildfire risk.

Measure 1.1.3 of the Climate Pact 2.0 asks every commune for a heat-stress analysis crossed with its vulnerable population — exactly what this page sketches at national scale. A full adaptation concept can be subsidised up to €25,000 (FCE circular 2025-050).