August Climate Data

Looking back at climate data for August, it was a very warm month indeed - the 3rd warmest on record for the state overall.  Only in 1977 and 2004 was the month of August warmer for Alaska as a whole.  It was also the warmest month of the 2023 summer relative to normal; there were only a few days in August that were marginally cooler than normal overall.

Regionally, the warmth was most unusual across the eastern interior, and southwestern Alaska was relatively cooler.  A major trough-ridge contrast explains the pattern; both the trough over the Aleutians and the ridge over western Canada (and SE Alaska) were quite strong for the time of year, and the circulation anomaly pumped a great deal of warm air northward into Alaska.

South-central Alaska saw yet another wet and cloudy month, and the Southeast had more rain than in the very dry July, but it was still drier than normal.  ERA5 and NCEI disagree on whether the Southeast Interior saw moisture relief, but Rick Thoman notes that rains were highly variable in that area; some places remained very dry.

The trend towards warmer conditions as summer progressed probably had at least some connection to the developing El Niño, because a ridge over southern and eastern Alaska, and northwestern Canada, is a typical feature when El Niño is occurring in August.  The map below shows the typical August 500mb height patterns during El Niño.

However, other aspects of the circulation pattern from eastern Asia to Canada were highly atypical for El Niño.  Notice the tendency for lower heights/pressure near the Sea of Japan: that's the opposite of what happened in August this year (see the first map in this post).  Also, most of Canada tends to be cooler than normal in August during El Niño (first map below), but in fact it was very warm across Canada's northern tier, and the record fire season just kept on going.  The heat over Japan and northern Canada was relentless this summer, and that certainly can't be pinned on El Niño.

A better explanation for the overall North Pacific - North America pattern is the ongoing negative PDO phase.  It's very unusual indeed for a negative PDO to persist as El Niño emerges, but this year the PDO has remained entrenched in the negative phase; and the warmth to the east of Japan has a lot to do with that (i.e. the warm SSTs there correspond to a negative PDO).

Here's the spatial (air) temperature pattern for August when the PDO is negative.  It doesn't line up with the warmth in the eastern Pacific this year, but otherwise it's not a bad match from Japan to northern Canada.  Texas tends to be hot too - and they had a really awful summer.

Rounding out the Alaska climate maps for August, it was cloudier than normal once again for western Alaska and the northern Gulf coast.  It was also relatively windy from the Bering Sea to the western and northern interior.

It's also interesting to note the very high humidity (dewpoint) for much of the state.  This goes a long way to explaining the extremely high overnight temperatures and therefore also the remarkably delayed autumn foliage in the Fairbanks area.

For future reference, I'll include maps below for climatological summer, June through August.  It was the second warmest summer on record for the North Slope, and third warmest for the eastern interior climate divisions, according to the NCEI data.  2004 still holds the summer temperature record by some margin for the state as a whole and for the west coast, interior, and North Slope, as well as the northeast Gulf and central and southern panhandle regions.  2019 was the warmest summer for south-central and southwestern Alaska.

Rainfall, wind, and cloudiness were all exceptionally high for the northern Gulf Coast and southwestern mainland, but Southeast had really quite a dry and sunny summer.

And finally, it's just interesting to note again the dramatic shift that took place in mid-July as the weather suddenly and belatedly turned very warm.