WEATHER · CLIMATE NORMALS · 1991–2020
Rotterdam Climate — Averages by Month
What the weather in Rotterdam, NLaverages across a standard 30-year period. Each month's figure is the 1991–2020 mean temperature and total rainfall from the ERA5 reanalysis — the long-run normal a place settles around, not a forecast for any particular day.
Month-by-month normals
| Month | Avg temperature | Avg rainfall |
|---|---|---|
| January | 3.9 °C · coldest | 68.1 mm |
| February | 4.2 °C | 57.9 mm |
| March | 6.6 °C | 58.6 mm |
| April | 9.7 °C | 53.5 mm |
| May | 13.2 °C | 66.3 mm |
| June | 15.9 °C | 69.7 mm |
| July | 18.0 °C · warmest | 85.3 mm |
| August | 17.9 °C | 85.4 mm · wettest |
| September | 15.0 °C | 76.1 mm |
| October | 11.3 °C | 74.9 mm |
| November | 7.4 °C | 72.0 mm |
| December | 4.7 °C | 77.3 mm |
How to read these numbers
These are reanalysis normals, not readings from a single weather station. They come from the ERA5 0.25° (~25 km) global reanalysis grid, sampled at the grid cell nearest Rotterdam — centred at 52.00°N, 4.50°E. A reanalysis blends observations with a physics model onto an even grid, so a coastal or mountain city's cell can read a little cooler, warmer, wetter or drier than the city centre itself. The month-to-month shape — when it's hot, when it rains — is what these normals capture best.
“Normal” means the 1991–2020 average, the current World Meteorological Organization standard period. A normal is what a place tends toward over decades — any single day, month or year can and will depart from it.