When Paris reaches 40 degrees Celsius and the official swimming zones along the Seine are not yet open, there is one answer: Canal Saint-Martin. This is where Parisians actually go to survive a heatwave, not the tourist guides, not the air-conditioned museums. The canal.

The scene on a hot day is unlike anything you see in Paris the rest of the year. People spread out along the stone banks with towels and bottles of water. Groups of young men climb the iron railings of the bridges and jump into the water below. It looks reckless and it probably is, but the exit is the hardest part. The canal walls are steep and smooth. Getting out requires finding one of the few metal ladders along the banks.

I jumped in. The water is cold, immediately and completely cold, which after an hour in 40-degree heat is the best sensation imaginable. The visibility underwater is zero, everything is dark below the surface, but the temperature is worth it.

One thing changed in 2026 compared to previous summers. A strict public alcohol ban was in place throughout the heatwave period. No drinking in the streets, no drinking by the canal, no alcohol sales from noon to midnight in nearby shops. The atmosphere was noticeably different, calmer, more family-oriented, less the famous Paris picnic culture and more a community gathering around water.

I left my bag on the bank while I swam, a social experiment I run occasionally in different cities. When I came back everything was exactly where I had left it. Canal Saint-Martin is not a place where you need to be particularly anxious about your belongings.

Go to Canal Saint-Martin during a Paris heatwave. Bring water, bring a towel, and if you are going to jump in, walk the banks first to find where the ladders are.