The first day of summer is marked by the summer solstice, or the longest day of the year. Here's what to know about summer 2025.

Summer officially begins Friday, June 20, at 10:41 p.m. Eastern time. That’s the precise moment of the summer solstice — making for the longest, brightest day of the year in the Northern Hemisphere. Temperatures are toasty and the humidity is sweltering across much of the Lower 48. There’s no denying it’s summer.

Summer's official start comes Friday with the summer solstice. Andrew Fraknoi, astronomy professor for the Fromm Institute at the University of San Francisco, joined CBS news to discuss the solstice.