Western Skagit County
... This is the driest and warmest time of the year...
The last 10 days of July and the first 10 days of August are the
driest and warmest time of the year in western Washington. Going
back 121 years when Seattle weather records began in 1893... the
average number of times it has rained on any given day in this 20-
day period is 13 times or only 11 percent in those 121 years.
It has rained but only 9 times in those 121 years on August 4th
making it the day with the lowest chance of rain in the entire year.
Even the best chance of rain on any day during this stretch is on
August 6th when it has rained 19 times... only a 16 percent chance.
Reviewing records at Seattle-Tacoma Airport that started in 1945...
July 29th is the driest day of the year with a total of only 0.31
inches recorded on that day in the 69 years of record.
This time period is also the warmest time of the year. Out of the
187 days with highs of 90 degrees or more at Seattle-Tacoma Airport
through 2013... 69 or 37 percent of those hot high temperatures have
occurred in this 20-day period.
The record for the number of consecutive days with highs 90 degrees
plus in Seattle is 5 - from August 7th through the 11th in 1981. The
record for consecutive days with highs 80 degrees or more is also
mainly in this time window... 15 days from July 30th to August 13th
1981. The day with the best chance of getting a high 80 degrees plus
is July 27th with 29 days out of 69 years or 42 percent.
Regarding the 10 warmest days of the year on average based on
average high temperatures... 8 of them are in this 20-day window. The
remaining two that are outside of the 20-day period are July 21st
and August 12th.
Given this is the driest and warmest time of the year... it is no
coincidence that seafair involves this time of year. OH and today -
July 29th - is when the warmest temperatures ever recorded in many
places around western Washington occurred in 2009. Sea-tac Airport
hit 103 degrees... Olympia 104... Bellingham 96 and Centralia 107