Surplus Of Summer Sun Sets Seattle Sizzling

SEATTLE - The old tongue twister goes: Suzie sells sea shells by the sea shore. That might also double as good advice on where to spend the next few days as we bake in the first real heat wave of the summer season.

During a usual Seattle summer day, we have our "natural air conditioning" in the form of a westerly wind that blows in off the Pacific Ocean. That keeps temperatures in the 70s.

However, Sunday and Monday, we have a strong thermal trough building into the area (read more about thermal troughs in our Weather FAQ) helping to pull our winds from the east instead of the usual west.

When winds come from the east (an "offshore" wind) that does a few things:

1) That air is coming from a much hotter Eastern Washington, so it's already got a head start in being warm.

2) As that air comes over the top and sinks down the Cascade mountains, it heats up even more (as air warms and dries out when it sinks, just like it cools and becomes more moist as it rises.) Forks on the coast also usually gets into the low 90s in this pattern as air sinks down the western slopes of the Olympic Mountains.

and 3) It holds back the west wind from coming in off the ocean to cool us off.

Add that all up, and we're looking at afternoon and evening temperatures around the Puget Sound area in the upper 80s and low 90s for Sunday -- and perhaps even mid 90s in the Cascade foothills where you're away from the water and closer to that hot air coming down the mountains. Seattle's record high for Sunday is 87 degrees set in 1992 and it is definitely nervous. Another tidbit: Seattle has not hit 90 in nearly two years -- it was Aug. 9, 2004 the last time it was over 90 (92). Seattle averages two days a year at 90 or warmer.

As a result, the National Weather Service has issued an Excessive Heat Watch for western Washington from Sunday afternoon through Monday evening. They are also warning of possible air stagnation problems through Tuesday, so those who are sensitive to air pollution should limit outdoor exposure.

You can track the current temperatures here:

Or if you don't see your town, try this link

At Least It's A Dry Heat

The good news is, unlike most of the rest of the country, when it does get hot here, it's more of a desert, dry California heat than a humid, sticky Midwest heat.

That's due to the fact that the air is already coming from dry Eastern Washington, and then dries out even more when it sinks down the western slopes (remember, the east winds hold that humid ocean air at bay offshore).

In the Midwest and East Coast, their muggy air comes up from the warm, moist Gulf of Mexico. So at least here it's easier to cool off by sweating or spraying some water on you as opposed to the oppressive heat of the Midwest and East coast.

Even Hotter for Monday

Believe it or not, it's expected to be even a little hotter for Monday, with everyone except for the coast into the 90s, and maybe upper 90s along the foothills as the offshore flow gets stronger still. The record high in Seattle for Monday is 88, and that too looks like it'll be rewritten. The coast, on the other hand, will start the cooling process and drop into the 60s or low 70s as cooler air finally begins to trickle in from the ocean.

The thermal trough is finally expected to move inland and to our east during the day Tuesday, allowing the cooling west winds to finally win the battle and begin their push inland.

That will allow for a little bit of cool air to begin mixing in Tuesday afternoon in the form of a seabreeze, allowing areas along the northern Olympic Peninsula and near the Strait of Juan De Fuca to drop back into the 70s.

But in the greater Puget Sound area, temperatures will likely already be solidly into the 80s by the time the cooler air begins to trickle in, so another pretty toasty day expected.

The cool winds are expected to rev up Tuesday night and push through the entire area, kicking in our "natural air conditioning". That might create some brief morning clouds for Wednesday but still plenty of sunshine. Highs will drop back into the mid-upper 70s as the air mass will still be residually warm enough for a warmer-than-normal day, but more manageable for most folks.

Marine flow strengthens for Thursday through the weekend, getting temperatures down closer to the normal low-mid 70s amid morning clouds and afternoon sunshine, which would be much more comfortable weather if you need to go and pick a peck of pickled peppers :)