Seattle is having the warmest May on record — and will probably tie for driest too

SEATTLE -- Thursday  is the last day of May and, with the current forecast, May will end up with an average temperature of a little above 61 degrees. This will make May 2018 the warmest May on record for Seattle.

The average temperature of each day is calculated by adding the morning low and the afternoon high, then dividing by two.

This is an old record. So far, the warmest May ever was in 1940 when the average temperature was 60.5 degrees. This includes information from the Federal Building in Seattle which goes back to the 1890s.

Significantly, since 2014, we have had the warmest February, March, April, June, July, October, November and December on record. For you weather geeks, here are the records with their dates, and the previous records.

Notice how old the previous records were:

  • February 48.8 (2015) old record 48.7 (1977)
  • March 50.5 (2015) old record 50.3 (1992)
  • April 56.7 (2016) old record 53.6 (1977)
  • June 67.7 (2015) old record 64.9 (1992)
  • July 71.2 (2015) old record 69.5 (2009)
  • October 58.0 (2014) old record 56.4 (1965)
  • November 50.9 (2016) old record 49.4 (1965)
  • December 45.3 (2014) old record 45.2 (1969)

For the months not on the list above, we had the SECOND warmest August and September last year:

  • 2nd warmest August 70.3 (2017) record 71.1 (1967)
  • 2nd warmest September 64.7 (2017) record 65.7 (1967)

Only January has not been the warmest or second warmest during the last four years.

We are on track to tie the record for the driest May ever with 0.12” of rain. This would tie the rainfall for May of 1992.

So far, the “Long-Range Prognostics” from the Climate Prediction Center show that June will be starting out with normal temps (upper 60s) and below-normal rainfall for the first week, and then probably go above-normal temp-wise after that.

Many thanks to Dana Felton of the National Weather Service for all the data cited above.