Summer started in The Netherlands on June 20 of this year 2024. That date varies every year. It is the longest day of the year. From now on the days will get shorter again. The seasonal differences arise from the tilt of the axis around which the Earth rotates. Indeed, we believe that the Earth is a sphere. Due to the inclined axis relative to the sun, the sun rises higher above the horizon in the northern hemisphere in summer than in winter. The sun therefore shines longer in the summer than in spring, autumn and winter.

The further north, the shorter the sun is above the horizon. Even within our national borders, the difference in day length is noticeable. In the area north of the Arctic Circle, the sun is not visible at all for a few months.

For practical reasons and according to international agreement, meteorologists use a different seasonal division to calculate climatological averages. The Societas Meteorologica Palatina is one of the first international weather organizations. This organization decided in 1780, under the leadership of the German Elector Karl Theodor, to regard three consecutive calendar months as one season.

Astronomical autumn starts around September 21 and meteorological autumn already on September 1. All seasons last exactly three months. Summer consists of the three warmest months (June, July and August), winter of the three coldest (December, January and February). Spring and autumn are in between.