Duration of daylight hours varies both by geographic location and season; for example, Key Largo, Florida, one of the southernmost cities in the U.S., can get up to 13 hours and 40 minutes of daylight in June and 10 hours and 37 minutes in December, while Barrow, Alaska, one of the northernmost cities in the U.S., experiences extremes of absolutely no daylight during winter months and 24 hours of sunlight in summer. The amount of sunlight a city receives depends more on latitude than longitude, with locales in the Arctic Circle, including Tromso, Norway and Murmansk, Russia experiencing seasonal extremes of daylight availability, while those along the Equator, including Quito, Ecuador and Nairobi, Kenya, have predictably even daylight hours year-round.
As illustrated above, daylight hours fluctuate wildly throughout the world based on location, and this is true within the United States as well thanks to the wide swath of space the country occupies between the Equator and the Arctic Circle. Key West's relatively minor difference in daylight hours, with just about 3 hours of difference between the longest and shortest days of the year, reflects the relative stability of seasons experienced in Equatorial locations. Thanks to seasonal tilts on the Earth's axis, Arctic locations can point either continuously toward or continuously away from the sun.