Summer in western Washington officially begins early Saturday morning, June 21, when the summer solstice occurs.
But our weather tends to lag what the calendar says. For much of western Washington, climatology (history of weather) shows summer usually begins in Seattle around July 12. Some years are earlier, others later, but generally the season appears to change on the 12th.
The start of western Washington’s summer weather is dependent on the position of the eastern Pacific high pressure area. By mid-July, the high usually establishes itself far enough north off the coast to deflect most wet weather systems north of Washington, meaning more sunshine, and the warmest and driest times of the year. That tends to last into September for the region.
Summer begins on the calendar this weekend and looking at the forecast, at least the first and second days of the official season will look summer-like with sunshine and temperatures reaching 70 degrees or more in many spots.
And in case you were wondering, there are two summer solstices – one for the northern hemisphere and the other for the southern hemisphere. For the northern hemisphere, Saturday is the point when the Earth’s tilt of its axis reaches its greatest inclination toward the sun. Another way to put it: Earth is leaning toward the sun at its highest point – just over 23 degrees north latitude.
For the southern hemisphere, Saturday is the start of winter. Their summer solstice is around December 21, the start of winter in the northern hemisphere.