What a Heat Wave Really Means to Meteo-France | RainViewer Blog

TL;DR: To Météo-France a canicule is not a temperature. It is a local threshold crossed several days in a row. Two thresholds per day, a daytime maximum and a night-time minimum, have to be exceeded together Thresholds are calculated department by department from local climate records The same temperature can trigger an alert in Brittany and not in Provence Nights matter as much as days: without night-time recovery, the health impact rises City centres cross the threshold before the rural communes next door A day at 35 C (95 F) is not automatically a heat wave.