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When are there jellyfish in France?

Portuguese man o' war are recorded most in January, February, September, November and December — and this is the one that matters, because the sting is severe.

Portuguese man o' war (severe sting)

Recorded well above the expected rate in January, February, September, November and December, peaking at 6.9× the expected rate. Based on 210 records.

MonthJanFebMarAprMayJunJulAugSepOctNovDec
Recorded vs expected 1.9 1.3 0.0 0.1 0.0 0.0 0.8 1.0 1.9 0.9 2.1 6.9

Mauve stinger (painful sting)

Recorded well above the expected rate in June, August, October and November, peaking at 1.5× the expected rate. Based on 2,050 records.

MonthJanFebMarAprMayJunJulAugSepOctNovDec
Recorded vs expected 0.4 0.2 0.3 0.7 1.0 1.4 1.1 1.5 1.2 1.3 1.3 0.9

True jellyfish (varies by species)

Recorded well above the expected rate in May, June, August and September, peaking at 1.6× the expected rate. Based on 5,292 records.

MonthJanFebMarAprMayJunJulAugSepOctNovDec
Recorded vs expected 0.3 0.2 0.3 0.6 1.3 1.4 1.2 1.6 1.3 1.2 1.0 0.7

Sea temperature in France

Records from GBIF, the Global Biodiversity Information Facility. How the adjustment works