Warm summer temperatures are augmented by essentially continuous sunlight and brief summer storms, while extreme winter cold spells are punctuated by long hours of darkness and little wind. The relatively dry climate supports abundant plant growth thanks to frozen subsoils and a low evaporation rate. Plant communities are also shaped by frequent summer storms that produce very little rain, but numerous lightning strikes. These “dry” storms cause numerous wildfires resulting from lightning strikes. Occasional flooding also shapes the landscape and creates habitat diversity.
The area has a short growing season, averaging 81 days at Fort Yukon, in the heart of the Refuge. The average date of the last killing frost in the spring is June 1; the average date for the first killing frost in the fall is August 21. However, this short growing season is punctuated by 84 days of continuous sunlight and twilight from May 13 to August 4; though officially in Fort Yukon the sun fails to fall below the horizon between June 5 and July 7. In the winter, the sun stays below the horizon for a large part of the day, but twilight lasts for several hours. The shortest day of the year, December 21st, known as the winter solstice, is graced by the sun’s presence in Fort Yukon from 11:35 a.m. to 1:44 p.m., a period of 2 hours and 9 minutes of sunlight.Temperature and precipitationFort Yukon holds the state record high temperature of 100° F (38° C), and comes close to the record low at –75° F (-59° C). This village is the largest within the refuge and has good historical climate records. For the period of January 1, 1938 through March 31, 1990 the following averages were recorded on the refuge:
More information, including current weather conditions for Fort Yukon, can be found at the http://forecast.weather.gov/MapClick.php?zoneid=AKZ220.
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More than 150 species of birds dominate the landscape during spring and summer.magnitude greater than that of other vireos.