Despite the almost summer temperature of +27 degrees recorded on September 9, the weather in Latvia switched to autumn mode the very next day. According to preliminary data from the Latvian Environment, Geology and Meteorology Centre, September 10 marked the beginning of meteorological autumn. There is a clear criterion for this: the average daily air temperature must remain below +15 degrees for at least five consecutive days. The first day of such a period is considered the start of the season. If on Monday the average daily temperature remains below this threshold, meteorological autumn will officially be considered to have begun on September 10. However, if the temperature reaches +15 degrees, the count will start anew, and the next possible date will be September 15. For most residents, this means not just a change of calendar. It is after the onset of meteorological autumn that the weather usually becomes more consistently cool, and the likelihood of a prolonged return of summer warmth significantly decreases. At the same time, this season cannot be called unusually early. According to the climatic norm from 1991 to 2020, meteorological autumn in Latvia on average begins on August 31, meaning it arrived later than usual this year. In recent years, the dates for the onset of autumn have varied significantly. For instance, in 2024, the necessary temperature criterion was met as early as August 20, while in 2023 a record was set — meteorological autumn began only on October 4. It is worth noting that there are several ways to define the seasons. The calendar autumn began on September 1, while the astronomical autumn will not arrive until September 23. The solar autumn, based on the duration of daylight, started on August 6. Meanwhile, long-term forecasts remain ambiguous. Earlier, the Copernicus program expected a warm and wet autumn for Europe with an increased risk of storms and flooding. However, more recent calculations from the European Centre for Medium-Range Weather Forecasts indicate that October and November in the Baltic region may turn out to be cooler and drier than previously anticipated. Thus, summer warmth in Latvia has seemingly already given way to stable autumn weather, although the final confirmation of the meteorological season will be known after processing the temperature data for Monday.
