The past couple of days were very warm across the interior, but yesterday was a very chilly day for the time of year in Alaska's northernmost town of Utqiaġvik. With a daily maximum temperature of 31°F at the airport, it was the latest sub-freezing day in "spring" since 1996, and the daily mean of 27.5°F ties with 1979 for the latest on record for such cold. Other than the same date in 1979, such a chilly day (mean temperature below 28°F) has not been observed before between June 22 and August 12.
Similar conditions were measured at the nearby high-quality CRN observing site, with a daily mean temperature of 27°F. This site's period of record only goes back to 2003, but the latest date with such chill was previously June 12.
There was also a little snow, and the late morning report of snow falling with a temperature of 26°F is the second latest on record for such conditions: the record is June 29, 1976.
One day's weather in isolation is not significant from a broader climate perspective, but nevertheless the chart below shows a striking contrast with the trend of recent decades: it shows the lowest daily mean temperature in the window June 15 - August 15.
As for a cause, there have been episodes of strong mid-atmospheric low pressure over the Arctic Ocean this month, and one of these troughs brushed past Alaska's Arctic coast in the past couple of days, bringing a cold air mass over the nearby ocean. A northerly breeze for most of the day yesterday, combined with heavy cloud cover, was enough to keep temperatures below freezing.
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