Summer Solstice 2025 United States. This is the longest day of the year and marks the start of summer in the northern hemisphere. Starts on march 20, 2025, at 11:06 pm and lasts until june 20, 2025, at 4:51 pm (93 days) summer:

The summer solstice heralds the beginning of summer. You can use the us holiday calendar and date calculator to plan this and other important national,.