Has autumn begun if it is still hot? Yes, according to the meteorological calendar. Confusion arises when we use one word for a climate classification, astronomy and the weather we feel outside. This guide concerns the Northern Hemisphere, where continental Europe lies; it is not a forecast or a bulletin of current warnings.
Two calendars for two different questions
Meteorological autumn: 1 September to 30 November. It covers three whole months, as explained in the KNMI guide to the seasons. It is the usual reference for autumn climate summaries.
Astronomical autumn: starts at the September equinox, usually on 22 or 23 September, and ends at the December solstice. The Met Office explains the distinction. Check the exact equinox date for the relevant year and time zone.
Why count whole months?
A fixed division makes statistics easier to compare across years. Imagine a report comparing September, October and November in two different years: it needs to use the same interval. If counting began on the first day someone considered chilly each year, the periods would differ. This example illustrates the calendar's usefulness; it is not an actual measurement.
The calendar does not switch on cold weather
The start of a season does not require the weather to change that day. Météo-France describes autumn as a season of contrasts, with mild and cold conditions alternating. A warm September afternoon therefore does not contradict the meteorological definition.
A three-month outlook cannot decide your Saturday
AEMET provides probabilistic seasonal forecasts. They describe scenarios for a three-month period, not a daily weather schedule. Météo-France explains their limitations: a quarterly average does not determine every day's weather.
Invented example: you read “a warmer-than-normal autumn” and organise a picnic for a particular Saturday. That phrase does not tell you whether rain will interrupt lunch. Nor does “wetter” mean you should cancel every weekend. The decision needs local information closer to the date.
Three checks for your plans
- Define the question: are you trying to understand a climate summary or decide when to go out? These are different needs.
- Make the plan specific: note the location, route and hours; “travelling around Europe in autumn” is too broad to select a useful forecast.
- Review relevant information: check the local forecast and official warnings shortly before departure. For Spain, our guide to AEMET warning colours explains how to read them.
Another practical example: a museum visit and an outdoor lunch may share a city and date but call for different backup plans. You do not have to base those decisions on the word “autumn”: relate the weather information to what you will actually be doing.
Which autumn is correct?
Both, provided you state the definition. For seasonal comparisons, clarify which months the summary includes; for a day out, look for a forecast. The calendar organises the year but does not replace weather information.
Educational guide reviewed on 3 September 2026. Cover: AI-generated illustration, not a photograph of a real location or weather event.