Bewolking — 2020
| Maand | Velsen | Heemskerk | Verschil |
|---|---|---|---|
| Jan | 79 % | 79.5 % | -0.5 |
| Feb | 73.3 % | 73.8 % | -0.5 |
| Mrt | 51.4 % | 52.2 % | -0.8 |
| Apr | 39.7 % | 40 % | -0.3 |
| Mei | 43.7 % | 44.8 % | -1.1 |
| Jun | 64.2 % | 66.1 % | -1.9 |
| Jul | 60.4 % | 61.8 % | -1.4 |
| Aug |
| – |
| – |
| – |
| Sep | – | – | – |
| Okt | – | – | – |
| Nov | – | – | – |
| Dec | – | – | – |