When does summer start?
Usually, when we talk about the first day of summer, we are referring to the astronomical summer which is defined by the Earth's axis and orbit around the Sun.
The astronomical calendar determines the seasons due to the 23.5° tilt of the Earth's rotational axis in relation to its orbit around the Sun. Both Equinoxes and Solstices are related to the Earth's orbit around the Sun.
This year, astronomical summer began on the 21st of June 2019 and ended on the 23rd of September 2019.
For upcoming years, the dates for astronomical autumn will be;
|Year||Summer Starts||Summer Ends|
|Summer 2019||Friday 21st June 2019||Monday 23rd September 2019|
|Summer 2020||Saturday 20th June 2020||
Tuesday 22nd September 2020
|Monday 21st June 2021||
Wednesday 22nd September 2021
|Tuesday 21st June 2022||
Friday 23rd September 2022
|Wednesday 21st June 2023||
Saturday 23rd September 2023
|Thursday 20th June 2024||
Sunday 22nd September 2024
However, meteorologists are also interested in the beginning of the meteorological summer. Meteorological summer will always begin on the 1st of June; ending on the 31st of August.
The meteorological seasons consist of splitting the seasons into four periods made up of three months each. These seasons are split to coincide with our Gregorian calendar, making it easier for meteorological observing and forecasting to compare seasonal and monthly statistics.
Solstices and equinoxes
Solstices and equinoxes are the astronomical transition points between the seasons and mark key stages in the astronomical cycle of the Earth. In a year there are two equinoxes (spring and autumn) and two solstices (summer and winter). The dates of the Equinoxes and Solstices aren't fixed due to the Earth's elliptical orbit of the Sun. The Earth's orbit around the Sun means that in early January, the Sun is closest (known as perihelion) and in early July it is most distant (aphelion).