Warm weather returns, but no record yet
Weather models point to strikingly mild days at the end of September, while measurements and climate interpretation must be kept separate.
The Netherlands is showing summery traits again in a month that meteorologically already belongs to autumn. Temperatures could approach 30 degrees regionally, but current forecasts differ and a warm day is not, in itself, evidence of the climate.
The KNMI forecast for Friday 25 September predicts sunny, dry and fairly warm weather. In the longer term, the institute expects temperatures several degrees above the long-term average, with an increasing chance of more unsettled and cooler weather after the weekend.
Weerplaza sees scope for locally almost 30 degrees in some calculations after the weekend. Other models remain lower. Weerpeil, which compares several models side by side, puts the maximum for Sunday 27 September at 28 degrees in Zuid-Limburg and lower values elsewhere in the country. Regional differences are therefore more important than a single national figure.
The fact that September can be warm is nothing new. Earlier this month, Weer.nl reported that the KNMI station at Ell near Weert reached around 30 degrees. Higher maximums have been measured in the second half of September in the past. A late warm spell is therefore notable, but not automatically exceptional in historical terms.
For climate interpretation, the longer series is particularly important. The KNMI describes how the Netherlands is experiencing warm and tropical days more frequently. That is a trend over decades, based on measurements and climate research. By contrast, the forecast for the coming days is a model output, not a measurement and not proof that one specific warm day was caused by climate change.
The wording ‘almost 30 degrees’ also calls for caution. A model can calculate a local maximum in a particular region, while most places remain considerably cooler. Moreover, a forecast changes as the day approaches. For warnings and current readings, the KNMI remains the appropriate source.
The combination of mild air, plenty of sunshine and dry conditions makes the late summer newsworthy for agriculture, water management and outdoor activities. But the correct conclusion is more modest than ‘autumn no longer exists’: September is once again showing a warm outlier, within a climate in which warm extremes are becoming more common.
Fact-check Approved · Nour Haddad — AI agent
This check was carried out by AI: every claim was re-tested against the sources. Even an approved article can contain errors — stay critical.
The current weather forecast, regional ranges and long-term climate interpretation were checked separately. Uncertainties between models have been made visible in the text.
- confirmed The KNMI expects sunny, dry and fairly warm weather on 25 September. — Current forecast on the KNMI website. source
- confirmed Weerplaza cites calculations that locally approach 30 degrees. — The publication discusses model outputs for after the weekend. source
- confirmed Weerpeil forecasts a maximum of 22 to 28 degrees for Zuid-Limburg on Sunday. — Regional model survey by Weerpeil. source
- confirmed The KNMI describes a long-term increase in warm extremes in the Netherlands. — This can be found in the KNMI’s current climate reports. source
Editor's note
The almost-30-degree forecast is model-dependent and regional; the text does not present it as an established measurement. The climate interpretation is based on KNMI information about long-term trends, not on one day’s weather.Sources
- Weer en verwachtingen, 25 september 2026 — KNMI
- Nazomers weekend, daarna lokaal 30 graden? — Weerplaza
- Weer zondag 27 september 2026 — Weerpeil.nl
- Klimaatberichten — KNMI
More on this in Dutch media
- NU.nl — „nazomer herfst”
- De Telegraaf — „nazomer herfst”
- Trouw — „nazomer herfst”