Astronomical autumn has begun in the Northern Hemisphere. The autumn equinox occurred on Wednesday at 03:05 Latvian time. At the same time, astronomical spring began in the Southern Hemisphere. During the equinox days, both hemispheres receive almost equal amounts of sunlight, so the length of day and night becomes nearly the same. However, in Latvia, the equality of day and night does not occur exactly on the day of the equinox. On September 23, the daylight is still about ten minutes longer than the night, and for the first time this autumn, the night will exceed the day in duration only on September 26. This is related to the peculiarities of astronomical calculations. The length of the day is determined taking into account the refraction of sunlight in the atmosphere, and sunrise and sunset are considered to be the moments when the upper edge of the solar disk appears and disappears, not its center. In the second half of September, the length of the day decreases particularly quickly — by almost 4 minutes and 46 seconds daily. This process will continue until December 21, when the winter solstice occurs and astronomical winter begins. For most residents, the later sunrises and earlier sunsets become especially noticeable right now. In the coming weeks, it will get dark significantly earlier in the evenings. From the perspective of the so-called solar winter, the darkest months of the year will last from November 6 to February 4. At the same time, solar autumn in Latvia begins annually on August 6, so astronomical autumn falls approximately in the middle of this period. Meteorological autumn begins according to a different criterion — when the average daily air temperature remains below +15 degrees for at least five consecutive days. This year, according to meteorologists, it began on September 10. According to the European Centre for Medium-Range Weather Forecasts, this week Latvia is expected to receive significantly more precipitation than the climatic norm. The following week, on the contrary, should be drier, and October as a whole may turn out to be warmer and drier than usual. In the longer term, specialists from the Copernicus program link the weather characteristics of the current cold season with the El Niño phenomenon. For Europe, this means an increased likelihood of a warm and wet autumn and winter, as well as an increased risk of storms and flooding. In Latvia, this winter, more rain and snow than usual is expected, and the coldest months may be February and March.
