The chances of hot weather moving into the region by the end of the week have increased and the National Weather Service now has placed Portland under an excessive heat watch beginning Thursday afternoon.

The weather service issues a “watch” when the risk of a heat wave has increased but its occurrence and timing is still uncertain. By Tuesday, the likelihood is very good, but the exact temps are still in flux.

But before we get to the watch, which is in effect from Thursday through Sunday, we’ve got a couple of really nice days in which temps will be seasonable and residents can get prepared for the upcoming heat.

Tuesday will start with some high clouds in Portland and then skies will gradually clear through the afternoon. The high should reach about 77 degrees.

Wednesday will be much the same with mid-morning clearing and a bit more heat. The daytime high temp will reach about 83 degrees.

Now is the time to plan on ways to cool your living space, or where you might go when temperatures move into the 100s. Metro area counties will generally open cooling shelters during high heat events, but those plans have not yet been announced.

By Thursday the ridge of high pressure moving into the region will be intensifying over the entire West Coast. The weather service says much of northwest and west central Oregon and southwest Washington will be dangerously hot, especially for those with health conditions exacerbated by the heat.

Temps of up to 110 degrees are possible. As of Tuesday morning, Salem seems to be an epicenter of heat with many models showing high probabilities of reaching 100 by Friday. One model shows a 36% chance of Salem reaching 110 degrees on Saturday.

On the Fourth of July temps will be hot, but likely the coolest we’ll see through Sunday. Highs in Portland should reach about 94 degrees.

By Friday, “sunny and hot” will be the words with highs reaching 100 in most metro locations. Overnight lows will cool to about 64, which will offer some relief, but some areas may not cool that low and those without cooling appliances will be affected.

Currently, Saturday comes out as the hottest day of the run with temps nearly 104 in Portland and a 20-40% chance of temperatures at or above 110 along the Interstate 5 corridor and especially near Hillsboro.

Current long-range forecasts show some cooling beginning Sunday with temps moving back down to the high 90s.