First day of summer may be the longest but not the hottest

The stars haven’t made their nightly appearance in Bettles, Alaska since mid-April when twilight overtook the darkness of night. Since then, the amount of daylight has been increasing at such a rapid pace that all I ever see is daylight--even at two in the morning. 

In the Land of the Midnight Sun (as much of Alaska is called during the summer), one can lose track of time easily when the sun doesn’t set. In Bettles, the sun doesn’t set between June 2 and July 9. That is one advantage of living above the Arctic Circle--endless daylight around the summer solstice. Actually it seems like endless daylight from the beginning of May until mid-August because even twenty hours of daylight seems endless. 

For the rest of the northern hemisphere, summer solstice (June 20 this year) marks the day with the greatest amount of daylight. Bonners Ferry will peak at 16 hours and 9 minutes of daylight, but will bask in that maximum day-length (when rounded to the nearest minute) from June 17 to June 24. 

On the summer solstice, the sun will be at its highest point in the sky and setting and rising at its most northerly points on the horizon. Additionally, the earliest sunrise and latest sunset will occur simultaneously on the summer solstice. In Bonners Ferry, the sun will rise at 4:42 a.m. and will set at 8:52 p.m. The earliest sunrise actually occurs for several days--from June 11 to June 20. Likewise, the latest sunset begins on June 20 and continues until June 29. 

While the first day of summer may be the longest day of the year, it definitely won’t be the hottest. Both April 12 and August 31 are the same number of days away from the summer solstice but a significant amount of snow can be on the ground on April 12 while a 90 degree heat wave can persist on August 31. 

Snow lingers in some basins of the Selkirk Mountains well after the summer solstice

The difference in temperatures is that the northern hemisphere is still warming up in April and releasing heat in August. The Earth’s oceans and atmosphere act as heat sinks and absorb the sun’s warm rays. During the longest days of the year, they absorb the most heat and then retain that heat. This retention makes July and August the hottest months of the year. 

After a certain point, more heat is lost at night than is gained during the day, causing the northern hemisphere to cool. This cooling trend continues until after the winter solstice when the days become longer and more heat enters the atmosphere. Similarly, the shortest day of the year isn’t the coldest, January and February are usually the coldest months. 

The Earth takes longer to warm up than it does to cool down--on a yearly scale and a daily scale. After sunset, the coolness of night quickly rushes in while the warmth of the morning sun slowly warms the land. The icy grip of winter takes a long time to break in the Arctic, but once the Midnight Sun prevails the snow and ice melt fast.

With the longest day of the year occurring on June 20, the hottest days of summer aren’t far behind. 

Note: Published in the Bonners Ferry Herald on June 14, 2012.