How to predict fog for photography
Morning fog forms when the air near the ground cools overnight until it can hold no more water, and no wind moves it. You can read most of that from the forecast the evening before.
Humidity
Look at the forecast humidity between 4 and 10 h. At airports in 14 European cities, mornings with a forecast humidity of 95% or more had mist (visibility under 5 km) 37% of the time. The other mornings had mist 6% of the time.
Wind, rain, cloud and dew point
The numbers below are only for the mornings with a forecast humidity of 95% or more. Of all those mornings, 37% had mist. The share was higher or lower depending on the rest of the forecast:
| Forecast | Mornings with mist |
|---|---|
| Wind under 4 km/h | 50% |
| Wind over 10 km/h | 15% |
| No rain overnight | 43% |
| More than 1 mm of rain overnight | 18% |
| Clear sky the evening before | 49% |
| Overcast the evening before | 33% |
| Evening temperature within 1 °C of the dew point | 48% |
| Evening temperature more than 4 °C above the dew point | 25% |
Time of morning
Mist is about as likely at any hour from 4 to 8 h. After 8 h it starts to clear. Of the mornings at the 14 airports that had mist at some hour between 4 and 10 h, 66% had mist at 7 h. At 4, 5, 6 and 8 h the share was almost the same (61 to 65%). At 9 h it was 55% and at 10 h 44%. When there was mist at 6 h, it was still there at 7 h 85% of the time, and at 9 h 63% of the time.
Mist stays longer in midwinter, when the sun rises later. From November to January, 53% of the mornings with mist still had it at 10 h. In October, February and March it was 34%.
Place
Fog is local. Heathrow has mist on 7% of mornings. Stansted and Luton have it on 27%. On 3 October 2026 the Tempelhof station in Berlin reported 300 m visibility at 7 h while Dahlem, a few kilometres away, reported no fog at all.
How often fog happens
How often thick fog happens (visibility under 1 km for two hours or more) depends on the city. Of the European cities on the forecast pages, it is rarest in Amsterdam and Berlin, on 4% of mornings from October to March, and most common in Milan, on 17%. Mist is usually two to three times as common.
On the forecast pages these signs are combined into one percentage for each morning.
The numbers are from airports in 14 European cities, on mornings from October to March since 2024. For each morning, the forecast from the day before was compared with what happened: whether the visibility measured at the airport was under 5 km (mist) or under 1 km (fog).