The real start of summer

Most folks consult their calendars to see when summer starts.  And it will be listed as approximately June 21st.  This is know as the start of Astronomical summer.  It's the date when the day is longest in the northern Hemisphere.  According to timeanddate.com, 21 June in Deer Park has 16 hours, 2 minutes, and 26 seconds of daylight.  But we all know that twilight lasts much longer than that.  Essentially, there's a glow on the northeast (for sunrise) and northwest (for sunset) horizon starting around 3am and ending close to 11pm, which is Nautical Twilight.

But why is the longest day the start of summer?  Seems like that should be the middle of summer.  But that's like saying noon is the hottest hour of day, which we know isn't the case.  The reason is that the earth keeps heating up faster than it can cool itself until the sun gets much lower in the sky, around 5pm.  The same is true for summer.  The Northern Hemisphere will continue to get hotter through July and even early August before it starts to cool down.

There is another definition of summer:  Meteorological Summer.  This is just simply June, July and August.  Nothing scientific, just convenient, and fairly accurate.

There have been other attempts to define summer, mathematically, meteorologically, and otherwise.  All of them come down to one truth: it depends on where you live.  The average high temperature in May in Phoenix, AZ is 95F.  Sounds like summer to me.  But May is clearly not a summer month in Washington.  This is due to the frequent cool air masses that come into our area during that time of the year.  Yes, we can have a few hot days in May (like we saw this year), but it doesn't last long.  Same can usually be said for June as well.

When I first arrived here in 1995, folks told me that summer doesn't start until after the Fourth of July.  Folks in Seattle determined that summer started there on the 12th of July.  That used to be more true than it is today, as our summers are getting hotter and longer.  But the overall idea is still the same: consistent hot weather doesn't usually arrive until late June or early July.

All that said, the summer of 2023 actually looks like it is starting as we speak.  Daytime temperatures are going to consistently reach the 80s and 90s for the foreseeable future, with no cold air masses in sight.  And it's likely to get hotter.

Here's this morning's weather map, showing a deep low off the California coast (a common feature this year), with another low that, as expected, has moved by our area to the south, too far to have any effect on us.  It's bringing yet more rain to eastern Montana, which has had a VERY wet spring this year.  You can also see the strong high pressure over Texas which is causing the current heat wave there.

By the middle of next week, the California low also moves onshore to our south.  It does bring with it some moisture, and that could bring a threat of showers to our area.
 

This midweek chance of rain will be in the form of hit and miss showers.  No guarantee of anyone getting rain.  But the U.S. ensemble model is showing decent chances of rain for Tuesday and Wednesday, even in central Washington.  The Canadian ensemble (not shown) also has a chance of showers, albeit not as high as the US ensemble.

By the end of the week, high pressure from the Pacific is building into the West, for warmer temperatures and dry weather.  Note that there are low pressure systems moving by to our north, in northern BC and the Aleutian Islands.  Also note that high pressure is still residing over Texas and the Gulf Coast states as their heat wave continues.

Looking well into the future, you can see a low over BC/Alberta.  This may cool our temperatures a bit with a dry, breezy cold front.  

A bigger concern is that the southern high is forecast to move to the desert Southwest.  This is a favorite summer location for this high.  If it decides to take up residence there, it could mean an extended period of hot temperatures for our area.  We'll have to keep an eye on that.  The Climate Prediction Center is also pointing to a hot start for July.