# Rising tropical night frequency in France

> Live situation record from CLSTR: https://clstr.news/situations/rising-tropical-night-frequency-in-france
> Updated: 2026-08-20T14:19:00.000Z. Sources: 4. Developments: 2.

France is seeing an increase in ‘tropical nights,’ which occur when temperatures do not fall below 20°C between sunset and sunrise. Historically limited to the Mediterranean coast, these nights have become a regular summer phenomenon affecting northern regions such as Brittany. This trend is linked to climate change, the urban heat island effect, and thermal inertia in buildings.

In Lyon, the situation intensified in mid-August 2026. Residents experienced extreme conditions with temperatures between 23°C and 25°C combined with humidity levels of 80% to 90%, resulting in heat index values between 32°C and 34°C. Meteorologists attributed these conditions to Mediterranean winds and cloud cover. This event marked the 30th tropical night recorded in Lyon since June 1, 2026.

## Timeline

### 2026-08-20: Lyon faces intense tropical nights due to high humidity

Lyon has experienced intense tropical nights with high humidity reaching 90%, causing heat index values of up to 34°C. This marks the 30th such night in the region since June 2026.

2 sources. https://clstr.news/cluster/lyon-faces-intense-tropical-nights-due-to-high-humidity

### 2026-08-15: France experiences rising frequency of tropical nights

France is seeing a rise in ‘tropical nights’ where temperatures stay above 20°C, disrupting sleep and affecting regions previously unaccustomed to such heat.

2 sources. https://clstr.news/cluster/france-experiences-rising-frequency-of-tropical-nights

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Cite as: Rising tropical night frequency in France. CLSTR, https://clstr.news/situations/rising-tropical-night-frequency-in-france