What is the longest period of daylight in the northern hemisphere?

The longest period of daylight in the northern hemisphere occurs during the summer solstice, typically around June 21. On this day, locations above the Arctic Circle experience continuous daylight for 24 hours, while other areas enjoy extended daylight hours. For example, cities like New York may see around 15 hours of daylight, while those further north, like Oslo, can experience up to 18 hours or more. This phenomenon results from the tilt of the Earth's axis, which allows the sun to remain above the horizon for longer periods in summer.