Where Is Summer?

The calendar and the daylight say it's summer now, but the weather isn't quite there yet.  Anchorage has only reached 60°F three times so far, the elevated interior cold spot of Chicken is still seeing hard freezes by night, and Fairbanks hasn't yet reached 70°F.

Here's the UAF statewide temperature index: it's been on a downward trend since late winter.

The lack of a 70°F day in Fairbanks (the highest so far is 67°F) is getting to be quite unusual, especially compared to the last 20 years.  We have to go back to 2001 to find the last time May failed to reach 70°F, and the latest first occurrence in the NWS/Weather Bureau era is June 7 (1937 and 1955).  (The UAF climate record has a June 9 first occurrence in 1968, and June 12 way back in 1911.)

There's a chance 70°F will occur tomorrow, but if not then it may be another week or more until the next good chance; so the record may be in some peril.

Why so chilly?  The mid-atmosphere (500mb) flow pattern has increasingly developed into a trough over Alaska, keeping cold Arctic-sourced air over much of the state.  Back in April there was a trough over the Bering Strait region, and the kink in the jet stream has persisted and shifted east as spring has advanced.  Here's the 500mb pressure pattern for 15-day periods from the first half of April through the latter half of May.

Summer's delay may not please everyone, but it's good news for the early fire season: less than 1000 acres have burned so far statewide.  It's a big contrast to the situation in Canada, where fires are raging under hot and dry weather.  This contrast is eerily reminiscent of 2023:

https://ak-wx.blogspot.com/2023/06/almost-zero-fire.html