Bewolking — 2020
| Month | Katwijk | Voorschoten | Difference |
|---|---|---|---|
| Jan | 78 % | 77.9 % | +0.1 |
| Feb | 73.4 % | 73.8 % | -0.4 |
| Mar | 52.7 % | 53.2 % | -0.5 |
| Apr | 38.5 % | 37.7 % | +0.8 |
| May | 45.1 % | 46.5 % | -1.4 |
| Jun | 65.3 % | 65.7 % | -0.4 |
| Jul | 61.2 % | 62 % | -0.8 |
| Aug |
| – |
| – |
| – |
| Sep | – | – | – |
| Oct | – | – | – |
| Nov | – | – | – |
| Dec | – | – | – |