The start of summer in the Northern Hemisphere varies depending on the context:
- Astronomical summer begins on the summer solstice. In 2025, this occurs on June 20 at 10:42 p.m. EDT. This is the day with the longest period of daylight in the year when the Earth's North Pole is tilted most directly toward the Sun. Astronomical summer lasts until the autumnal equinox, around September 22 or 23.
- Meteorological summer is defined differently by meteorologists for consistency in weather records and starts on June 1 , lasting through August 31. This division matches the calendar months for statistical ease.
So for 2025, the official astronomical start of summer is June 20 in the Northern Hemisphere, while meteorological summer begins June 1.
