Where to Beat the Heat

The record heat wave of 2021 in the Pacific Northwest brought to light an unusual aspect about our area: the lack of air conditioners.  Certainly, most new homes in the Northwest are now outfitted with A/C.  But a lot of older homes don't have the cooling comfort of A/C.  How is common is that in the US?

A study back in 2020 by the Energy Information Agency determined the following facts:

• 89% of US homes have some form of Air Conditioning (central or window unit).
• Ignoring Alaska, the state of Washington had the lowest percentage of homes with A/C.  Only 53%.  That's probably higher now after the 2021 heat wave.
• Hawaii surprisingly only had 57% of homes with A/C.
• The rankings of the lowest percentage of A/C homes is as follows:

1. Alaska - 7%
2. Washington - 53%
3. Hawaii - 57%
4. Montana - 65%
5. Vermont - 67%
6. Maine - 70%
7. Wyoming - 71%
8. California - 72%
9. Oregon - 76%
10. New Hampshire - 78%
11. Idaho - 81%

The obvious pattern is that some of the states are located in the northeast, but the majority are located in the West; in the Northwest to be more specific.  At first glance that may make sense, given that these are the northern states.  But so are the Dakotas, Minnesota, Wisconsin, and Michigan, and they're not at the top of the list.  Here's a map to better visualize it.

So why is Washington so low on the list of AC homes?  Obviously a big reason is that the major metro areas of the state (Seattle, Tacoma, Olympia) are often cooler during the day due to the influence of the marine air.  Here's a national map of the average high temperature for July in the US.  Western Washington kinda sticks out as an anomaly.  And you can also see some light green shading in the Northeast.  The cool coastal water is also what puts California on the list, with the major metro areas of the Bay Area, LA and San Diego benefiting from this cooling.

But there's another, less obvious reason, that many of the western states are living without AC.  That has to do with the nighttime temperatures.  Here's the map of average overnight lows in July.

Notice all of that light green shading in the Northwest?  That's for average July low temperatures of 49-52F.  Compare that areas east of the Rockies.  Even the northern states of the Midwest and Northeast US don't cool below 50F in the summer, on average.  Oh, and all that red color in the southern states is just merciless.  Some parts of the Gulf Coast in Texas and Louisiana don't cool below 75F at night on average.  Hard to live there without AC.

The nighttime temperatures play a big role in heat waves.  Allowing the house (and its contents) to cool off at night makes a huge difference.  Opening the windows at night lets everything (walls, furniture, etc) cool down, and then closing the windows during the day keeps the cool air in.

It turns out that our Inland Northwest is one of the coolest places overnight in the summer.  There are of course some caveats to that statement.

• Urban areas are warmer.  This isn't just large cities like Spokane.  If you live in the city limits of Colville or Sandpoint it's going to be a little warmer than outside of town.
• The mountains will in general be cooler, as the map above shows.  But at least in the Northwest, not a lot of people live in areas above 4000' elevation.

So why is the Northwest one of the coolest places overnight?  Two reasons.  First, is humidity.  At night when the earth is cooling down, the heat is radiated up into the atmosphere.  If there is a lot of moisture in the atmosphere (i.e. humidity), that moisture absorbs some of the heat and radiates it right back down to the earth.  It acts like a blanket. So east of the Rockies, the earth can't cool off as well. Second is latitude.  The sun angle is so high in the sky in the southern states that the ground really heats up.  So during the night, the earth just can't radiate all of that heat back into space.

In the Northwest, we have both things working in our favor.  We have a dry climate (which is why all of the grass turns brown), and we're at a northern latitude.  In the Southeast, it's just the opposite.  They have neither effect working in their favor.

I took a look at the normal July low temperature in a number of towns and cities in our area.  Here's a sampling of what I found:

• Deer Park - 48.4
• Spokane - 57.6
• Boners Ferry - 53.2
• Chewelah - 48.8
• Colville - 52.6
• Davenport - 47.9
• Kellogg - 50.5
• Newport - 50.5
• Northport - 50.7
• Republic - 46.5
• Sandpoint - 51.6
• Wilbur - 50.0

Now compare that to some other locations in the Northwest:

• Seattle - 56.8
• Olympia - 50.7
• Portland - 57.9
• Astoria - 53.9
• Missoula - 51.5
• Kalispell - 47.6
• Butte - 45.9
• Boise - 61.9
• McCall - 47.2
• Baker City - 48.9
• Stanley, ID - 38.7 (yes, you read that right)

Finally, here's a sampling of average July low temperatures in other parts of the country.

• Bismarck, ND - 57.9
• Boston - 66.0
• Burlington, VT - 62.4
• Buffalo, NY - 63.1
• Caribou, ME - 56.3
• Cheyenne, WY - 56.1
• Denver - 60.2
• Duluth, MN - 56.2
• Green Bay, WI - 60.1
• Minneapolis, MN - 65.3
• Marquette, MI - 54.5
• San Francisco - 55.3

You get the idea.  Even the cold states of the upper Midwest and Northeast don't have overnight lows anywhere near the Northwest.

There are two weather elements that will ruin our natural nighttime air conditioning: clouds and/or wind.  Any kind of clouds will also act as a blanket at night, keeping us from cooling down.  Wind will also inhibit cooling, as the cool air near the surface is mechanically mixed by the wind with much hotter air a little bit above the surface.  A sudden burst of wind in the middle of the night can raise a temperature from the 60s back into the 90s.

During these heat waves, one place you don't want to go at night is the mountains.  While cooler than the valleys during the day, the mountains don't cool off at night.  This morning was a good example, where it was 52F in Springdale and 74F on Mount Spokane.