Bewolking — 2020
| Month | Katwijk | Wassenaar | Difference |
|---|---|---|---|
| Jan | 78 % | 77.7 % | +0.3 |
| Feb | 73.4 % | 72.8 % | +0.6 |
| Mar | 52.7 % | 52.1 % | +0.6 |
| Apr | 38.5 % | 37.9 % | +0.6 |
| May | 45.1 % | 44.4 % | +0.7 |
| Jun | 65.3 % | 62.8 % | +2.5 |
| Jul | 61.2 % | 59.2 % | +2.0 |
| Aug |
| – |
| – |
| – |
| Sep | – | – | – |
| Oct | – | – | – |
| Nov | – | – | – |
| Dec | – | – | – |