Heat Wave Ends

This summer's only significant heat wave has now ended in Alaska, and autumn is most definitely just around the corner.  But what a heat wave it was in the past week - a very unusual spell of warm weather that completely defied the character of the rest of summer and indeed the rest of the year so far.

My last post mentioned temperature records at Juneau and Uqiaġvik, but there's more to talk about.  The heat situation escalated significantly in Juneau on Friday, when the high temperature reached a remarkable 85°F - a new record for August and the latest date with such heat by more than a month.  Previous dates with 85°F or higher at Juneau airport have all occurred between mid-June and early July.

I also overlooked a similar record in Haines on Friday: 87°F, again easily the latest date with such a high temperature.  Only once, in 2017, has Haines reached 87°F in August, and that was on the 5th of the month.

Having said all this, mid-August 2004 was a close second for late heat in both locations: Haines reached 86°F then, and Juneau saw 84°F, just one degree lower in both places.

Here's a map view of high temperatures reported on Friday (August 14) across the northern Southeast (click to enlarge):

It was also very hot in the far southeast: Klawock airport measured 88°F (marked as 87°F on the map below - a data rounding issue).  This is a new August record by a margin of 4°F at Klawock, but data only goes back to 1998.  Nearby Ketchikan saw 89°F in mid-August 1977 and 87°F in mid-August 1950, so this kind of late summer heat isn't unprecedented in this area.

Emphasizing again the nearly statewide nature of the heat wave, Kotzebue broke a high temperature record on Sunday: 75°F, compared to a previous record of 69°F on that date.  Kotzebue has rarely seen such warmth after the middle of August, with the 2004 heat wave being the most notable such event in the past.

Referring back to UAF's statewide temperature index again, the value peaked at about 9.8 on Friday and Saturday, implying a statewide anomaly higher than about 99% of all days.  The last time it was this unusually warm (compared to normal for the time of year) was January 2025.

Here's a map of the standardized 850mb temperature anomaly in the last 7 days, illustrating the Alaska-centric nature of the feature.

Contrast the 30-day anomaly from late June through late July: