The sun's rays are as strong now as they are in August. So why are temperatures so cool? | KNKX

The sun's rays are as strong now as they are in August. So why are temperatures so cool?

Apr 24, 2020

After a pretty long dry spell, April showers have returned to the Puget Sound region. We’ve entered a typical phase of showers and sun breaks, with lots of instability in the atmosphere that produces dramatic clouds with light blazing through them. 

These are not the overcast skies that block the sun for days in winter or often mid-summer (when we get the dreaded "June Gloom.")

KNKX weather expert Cliff Mass says, in fact, the sun’s rays right now are as strong as they are in August, the height of summer, when we get our highest temperatures. Yet the temperatures remain quite cool. 

“Stunning, but true,” Mass said. “It’s not the sun that is keeping our temperatures down, it’s the time of the year.”

He says right now we’re about a month past the vernal equinox, just as in August we’re nearly a month from the vernal equinox. So the sun’s proximity to the earth — and its resulting strength — is about the same. The difference now is that the atmosphere and surface elements have not yet had a chance to absorb the heat.

“You can think of the atmosphere like a big flywheel, that you can start revving up the force on,” he said.

As that happens, the atmosphere, oceans and big water bodies like Puget Sound and Lake Washington, absorb the heat. But it takes a while.

“Even though the sun now is quite strong and it will be the strongest during the latter part of June, the warmest temperatures won’t be until early August, after the atmosphere has caught up,” He said.

Mass says a similar idea applies to our daily high temperatures: even though the sun is strongest at noon or 1 p.m. (depending on whether we’re in daylight saving time or not), the warmest temperatures for the day don’t come until 4 p.m. at the earliest — and more often at 5 or 6, from April through August, Mass says.

“So, it’s the same basic story," he said. "The sun revs up in the morning, but it takes a while for the atmosphere to catch up.”

CLIFF’S FORECAST

Mostly showers through Monday, although Friday offers a reprieve with dry weather and temperatures in the low 60s. Saturday a strong Pacific front comes through, bringing a half- to three-quarters of an inch of rain and temperatures dropping to around 60. Sunday offers the best chance for outdoor pursuits, with just some sprinkles in the morning and temperatures back in the lower 60s. Sunday night, another front comes through, bringing rain at least through mid-day Monday.