what is the day length at the north pole in summer
Daytime Near the poles, which coincide with the rotational axis of the Earth as it passes through the surface, the seasonal variations in the length of daytime are extreme. In fact, within 23.5째 latitude of the poles, there will be at least some days each year during which the sun never goes below the horizon. There will also be days when the sun never rises above the horizon. This number will be fewer, but close to the number of days in the summer where the sun doesn't set (for example the sunrise is usually a few days before the spring equinox and extends a few days past the fall equinox). This phenomenon of more daylight than night is not unique to the poles. In fact, at any given time slightly more than half of the earth is in daylight. The 24 hours of summer daylight is known as the midnight sun that is famous in some northern countries. To the north, the Arctic Circle marks this 23.5째 boundary. To the south, the Antarctic Circle marks the boundary. These boundaries correspond to 66.5째 north or south latitude, respectively. Because the Sun's disc itself is about half a degree in diameter and is very bright, truly dark days during which the sun never seems to rise are only seen beyond 72째 north or south latitude.
Daytime At middle latitudes, far from both the Equator and the poles, variations in the length of daytime are moderate. In the higher middle latitudes where Montreal, Paris and Ushuaia are located, the difference in the length of the day from summer to winter can be very noticeable: the sky may still be lit at 10 pm in summer, but may be dark at 5 pm in winter. In the lower middle latitudes where Southern California, Egypt and South Africa are located, the seasonal difference is smaller, but still results in approximately 4 hours difference in daylight between the winter and summer solstices. The difference becomes less pronounced the closer one gets to the equator. An approximation to the monthly change can be obtained from the rule of 12ths. With 4 hours change over the six months from winter to summer the day lengthens by about 4*1/12 of an hour (20 mins) in the first month, 4*2/12 (40 mins) in the second month, 4*3/12 (1 hr) in the third month, then 1 hr, 40 mins and 20 mins in the fourth, fifth and six months.