The month that has the longest day of the year in the Northern Hemisphere is June. This occurs around the summer solstice, typically on June 21st or 22nd. During the summer solstice, the North Pole is tilted closest to the Sun, resulting in the longest period of daylight for those living in the Northern Hemisphere. This astronomical event marks the beginning of summer, and many cultures celebrate it with festivals, rituals, and activities that honor the warmth and abundance of the season.