Astronomical Autumn Begins Wednesday — Nights Will Soon Outlast Days

Astronomical autumn will begin in the Northern Hemisphere on Wednesday, September 23, while the Southern Hemisphere enters spring, according to timeanddate.com. This year's equinox falls at 3:05 a.m., the moment when both hemispheres receive roughly equal amounts of sunlight and warmth, making day and night nearly the same length everywhere on Earth.

In Latvia, however, daylight on September 23 will still last about ten minutes longer than night. It won't be until September 26 that night first becomes longer than day this autumn. This slight lag occurs because sunrise and sunset times are calculated based on the moment the upper edge of the sun's disk appears or disappears at the horizon, accounting for atmospheric refraction, rather than the sun's center.

Days Keep Shrinking

The second half of September marks the fastest rate of daylight loss all year, with days shortening by about four minutes and 46 seconds daily. This shrinking will continue until December 21, the winter solstice, which marks the start of astronomical winter.

The darkest three months of the year, known as solar winter, will run from November 6 to February 4. Solar autumn in Latvia runs annually from August 6 to November 5, meaning the start of astronomical autumn falls right in the middle of that period. Meteorological autumn, which begins once the average temperature stays below +15 degrees for at least five consecutive days, arrived in Latvia this year on September 10.

Outlook for Autumn and Winter

According to the latest data from the European Centre for Medium-Range Weather Forecasts, air temperatures in Latvia are expected to remain above average through the first half of October. Next week is expected to bring more precipitation than usual, though the following weeks could be drier.

According to the European Union's Copernicus programme, an El Niño effect means Europe overall can expect warm, wet conditions this autumn and winter, with an elevated risk of flooding and storms. Latvia could see unusually heavy rain and snowfall in winter, with February and March potentially being the coolest months.