"At 5pm this afternoon, Anchorage International Airport officially hit 90 degrees for the first time on record," tweeted the National Weather Service (NWS) late Thursday.

The previous record was 85 degrees, set in June 1969.

The average high temperature for July 4 in Anchorage, located in southern Alaska, is a far cooler 65 degrees.

"Several all-time high temperature records were set at official observation sites throughout southern Alaska," the agency added Friday.

The abnormally warm weather is being caused by a "giant ridge of high pressure sitting right over us," NWS meteorologist Bill Ludwig told the Anchorage Daily News.

Alaska had earlier broken temperature records throughout a hot spring, particularly in the Arctic zone which is especially sensitive to climate change.

According to scientists, Alaska is warming at twice the rate of the global average.

"From 1901 to 2016, average temperatures in the mainland United States increased by 1.8 degrees Fahrenheit... whereas in Alaska they increased by 4.7 degrees," Rick Thoman, a climate specialist at the Alaska Center for Climate Assessment and Policy, told AFP in April.