Seattle sizzles for second straight day

SEATTLE -- There's breaking a record high for a day...

And then there's smashing it to bits.

Seattle will do the latter to its record high for July 1 as our third day of hot weather peaks across much of Western Washington Monday.

Seattle's record temperature is 87 degrees, set back in 1995, and with a high expected near 90, we'll blow that number out of the ballpark.

(Then again, Mother Nature is pretty much giving us a softball down the middle of the plate. Most record highs around this time of year are in the low-mid 90s, but for some reason, July 1 had never been warmer than the mid-upper 80s. It was the only other July day besides the 8th that had never seen 90. Now the 8th will be all alone.)

The hottest temperatures will be in the Western Washington interior from Everett south through the Puget Sound region and Southwestern Washington to the Oregon border where highs should climb into the upper 80s and low 90s. The National Weather Service has issued an Excessive Heat Warning through 11 p.m. for the Seattle, Tacoma, Everett metro areas and a Heat Advisory for Southwestern Washington.

And even nighttime darkness has provided little relief for those whose homes and apartments are baking without air conditioning. With muggy air in place, the temperature Sunday night only dropped to 67 degrees, obliterating the record for warmest low on July 1 which was previously 60 degrees.

If you need relief, head to the coast or Northwestern Washington where some marine air will provide a bit of cooling. Highs along the coast and north Olympic Peninsula are expected to top out in the mid 70s to low 80s while the I-5 corridor north of Everett will reach the low-mid 80s.

The heat was too much for one road in Renton, where 128th Street buckled and was down to one lane near 168th Avenue.

The early summer heat is related to the scorching heat wave gripping much of the interior western United States. Normally, for the Puget Sound region to reach the 90s, we need the aid of some easterly winds from a thermal trough that get additional warming as they sink down the Cascade Mountains. But this time around, there is no thermal trough to be seen and no easterly wind. Typically, this kind of pattern would give the Seattle area highs in the mid 80s or so but the air mass is so hot right now, we're getting into the 90s without any east wind boost. (Had the thermal trough been here, Seattle could have been looking at near or above triple digits today.)

The trade-off for not having the east wind is that the air is a bit muggier than usual so it feels even a bit warmer than a typical dry, low 90s kind of day would normally feel around here.

This ridge will very slowly weaken through the week, allowing a gradual increase in marine breezes each day and, in turn, a gradual cooling trend. Tuesday should be about 5 degrees cooler into the low-mid 80s as a little of our "natural air conditioning" kicks in, but the cooling will be more pronounced along the coast and north interior where high temperatures will drop to the low-mid 70s on the coast and mid-upper 70s north.

Highs will continue to drop through the week as a weak system will help to flatten the ridge of high pressure and continue to increase our marine breezes. Highs will drop to around 80 on Wednesday and then down into the mid-upper 70s for the July 4th holiday with some morning clouds but plenty of afternoon and evening sunshine.

Long range modes keep things pretty Seattle-typical the balance of the holiday weekend with morning clouds then sunshine and highs in the more comfortable 70s.