This September, average monthly temperatures in Bulgaria are expected to be above the usual range, which typically varies between 17 and 20 degrees for most of the country and between 3 and 10 degrees in the mountains. The highest temperatures are forecasted to reach between 32 and 37 degrees, while the lowest could drop to between 7 and 12 degrees, with slightly higher lows along the Black Sea coast.

Precipitation levels for the month are expected to be around the norm, which ranges from 40 to 60 liters per square meter in the plains and from 60 to 80 liters per square meter in mountainous and sub-mountainous areas.

The first ten days of September will mostly see sunny weather, with temperatures higher than usual. There is a greater likelihood of cumulus clouds and rain in the eastern regions during the early days, and more widespread precipitation is anticipated around the middle of the period, according to Anastasia Kirilova, a forecaster at the National Institute of Meteorology and Hydrology.

During the second ten-day period, there will be more days with a higher chance of rainfall, although temperatures will remain above average. The period will begin and end with dry, sunny conditions.

In the final ten days of September, temperatures are expected to stay relatively high, with mostly sunny weather. There will be occasional increases in cloud cover, particularly in the afternoon and in mountainous areas. There is a higher likelihood of more significant cloudiness and precipitation across the country during the first half of this period.

In September, the intensity of atmospheric circulation over Europe weakens due to the reduced thermal differences between the ocean and the land, leading to increased climatic drought in Bulgaria. However, in some years, precipitation can significantly exceed monthly norms.

Typically, cloudy days in September range from two to six, with about four days of rain. The month can also experience extreme temperatures around 40 degrees, while frost conditions can develop in the high fields during the second half of September.

At the beginning of September, the sun rises in Sofia at 6:52 a.m. and sets at 8:00 p.m., giving a day length of 13 hours and 8 minutes. By the end of the month, sunrise shifts to 7:23 a.m., and sunset to 7:09 p.m., reducing the day length to 11 hours and 46 minutes.

The autumnal equinox will occur on September 22 at 3:43 p.m., marking the beginning of astronomical autumn.