This May was wetter, cooler than years past

An inch of rain May 21 led a total of 2.2 inches of precipitation over nine days and pushed the month’s total to 2.9 inches. That provided seven of the 10 days of measurable downfall. It is a marked contrast to last year’s 0.6 inches of rain.

May’s rain total is 31% above the century average. This is the seventh wettest May since 2000. The six wetter years were each 3 or more inches, with only 2020’s 3 inches in the last 10 years.

For the year, the 15.3 inches of rain is half an inch above the average for 2000-2024 and 8.6 inches, 78%, above 2023’s rain January-May.

Temperatures were a bit cooler than normal, with the average daily average of 54.7 degrees almost 1.5% below the century average. That was the same for the average minimal temperature of 46.2 degrees being 1.6% below that average and the average daily high of 63.7 degrees being 1.7% below the century average.

The highest temperatures were the period May 10-12, all above 70 degrees, with 77.7 degrees May 11 the month’s high. After a 70.9 degree day May 15, high temperatures ranged from the mid-50s to the 66.5 degrees on May 31.

A record low was set for May 31, when the temperature dipped to 39.8 degrees

Calculations are based on 23 years of data with no records for 2006 or 2009.

Monday morning KNKX radio in Seattle reported Sunday’s all day rain, with tree limbs down and at least 15,000 customers without electricity, with WSU weather stations in Seattle and Snohomish each listing 0.31 inches of rain Sunday. Another 0.40 inches fell between midnight and 4 a.m. Monday at the Seattle station.

Measurements and data are at Washington State University’s Mount Vernon weather station on Memorial Highway.

May rain report

Rainfall last week,

May 26-June 1: 0.80”

Rainfall in May: 2.89”

Number of rain days: 10

Least rain, one day: 0.01”, 16th

Most rain, one day: 1.0”, 21st

Year least rain: 0.35”, 2018

Year most rain: 4.57”, 2010

Avg. rainfall, 2000-2024: 2.2” *

Rainfall, April: 2.6”

* 23 years: no data for 2006 and 2009. WSU Mount Vernon.