Temperatuur — 2020
| Mois | Haarlem | Velsen | Différence |
|---|---|---|---|
| Jan | 6.9 °C | 7.2 °C | -0.3 |
| Fév | 7.2 °C | 7.3 °C | -0.1 |
| Mar | 6.8 °C | 6.9 °C | -0.1 |
| Avr | 10.1 °C | 9.6 °C | +0.5 |
| Mai | 12.3 °C | 12 °C | +0.3 |
| Juin | 16.4 °C | 15.9 °C | +0.5 |
| Juil | 16.7 °C | 16.8 °C | -0.1 |
| Aoû |
| – |
| – |
| – |
| Sep | – | – | – |
| Oct | – | – | – |
| Nov | – | – | – |
| Déc | – | – | – |