Climate averages 1991–2020
Alphen aan den Rijn weather
in September.
A mild, moderately wet month: the 4th warmest and the 9th driest of the year.
Long-term climate patterns, not a forecast for a particular trip.
September is a mild month in Alphen aan den Rijn: daytime highs average 18.3°C and nights cool to about 12.1°C. By daytime temperature it is the 4th warmest of the 12 months.
Expect about 81 mm of rain on roughly 13 days, which makes September a moderately wet month (the 9th driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 43 min on an average September day.
The nearest other city in this atlas is Leiden (12 km away). In September its highs average 18.0°C, about as warm as Alphen aan den Rijn, with 87 mm of rain.
Among the 44 cities listed in the Netherlands, Alphen aan den Rijn ranks joint 25th of 44 for the warmest September highs and joint 37th of 44 for the driest September (rainfall, lowest first). The mean September high of those 44 cities is 18.4°C; Alphen aan den Rijn is 0.1°C cooler than that mean.
From September to October, average highs fall by 4.1°C to 14.2°C, and monthly rainfall rises from 81 mm to 84 mm.
The annual picture
September in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
Alphen aan den Rijn climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 5.9°C1.7°C | 1.7°C | 69 | 13.3 | 8.38 h |
| February | 6.6°C1.5°C | 1.5°C | 56 | 11.1 | 9.910 h |
| March | 9.6°C3.2°C | 3.2°C | 55 | 11.2 | 11.812 h |
| April | 13.3°C5.6°C | 5.6°C | 49 | 10.7 | 13.914 h |
| May | 16.7°C9.2°C | 9.2°C | 62 | 10.9 | 15.716 h |
| June | 19.3°C12.1°C | 12.1°C | 66 | 11.7 | 16.717 h |
| July | 21.4°C14.4°C | 14.4°C | 83 | 13.4 | 16.216 h |
| August | 21.3°C14.5°C | 14.5°C | 90 | 13.3 | 14.715 h |
| September, selected | 18.3°C12.1°C | 12.1°C | 81 | 12.8 | 12.713 h |
| October | 14.2°C8.8°C | 8.8°C | 84 | 13.7 | 10.711 h |
| November | 9.6°C5.3°C | 5.3°C | 75 | 14.1 | 8.99 h |
| December | 6.4°C2.5°C | 2.5°C | 79 | 14.0 | 7.88 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Leiden in SeptemberThe Netherlands · 12 kmHigh 18.0°C · Low 12.9°C · 87 mm rain
- Gouda in SeptemberThe Netherlands · 13 kmHigh 18.4°C · Low 12.0°C · 67 mm rain
- Zoetermeer in SeptemberThe Netherlands · 14 kmHigh 18.3°C · Low 12.5°C · 69 mm rain
- Hoofddorp in SeptemberThe Netherlands · 19 kmHigh 17.9°C · Low 13.0°C · 81 mm rain
- Amstelveen in SeptemberThe Netherlands · 24 kmHigh 18.1°C · Low 12.3°C · 81 mm rain
- Delft in SeptemberThe Netherlands · 25 kmHigh 18.3°C · Low 12.5°C · 74 mm rain
- The Hague in SeptemberThe Netherlands · 25 kmHigh 18.1°C · Low 13.0°C · 74 mm rain
- Rotterdam in SeptemberThe Netherlands · 26 kmHigh 18.5°C · Low 12.0°C · 69 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for Alphen aan den Rijn) is explained once on the Alphen aan den Rijn year overview and on the Sources, method and limits page.
Hoofddorp and Amstelveen lie in the same rainfall cell, so their rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.