First frost map

The median date of the first autumn frost (below 0 °C) in 1079 cities, from ten years of hourly weather data. Each dot is a city, coloured by the month the first frost usually comes; in the southern hemisphere autumn starts in March, so its cities are coloured by the same season. 412 cities had no frost in ten years.

• Earliest first frost in the north: Iqaluit, 3 September
• Latest first frost in the north: Tlemcen, 1 January

• Frost-free season in 1076 cities
• Frost dates by city

Median dates of the last frost below 0 °C in spring and the first in autumn, 2016–2025, from ERA5 hourly data (Open-Meteo) for each city's grid cell; the frost-free season is the days between them. The same rules as the Greenly app.