Indeed, the NW flow of chilly, damp Alaska Gulf air into the PNW won’t let go.  Refill that Mug to warm up this discussion.

This week.  Cool pattern remains in place, with a break on tap for mid-to-late week.  Showers, possible thunderstorms and lots of cloudiness is the forecast for today, Monday May 12.  Not too damp over the Puget Sound though, as that pesky Low slowing fills in over southern OR.  Showers will diminish a fair amount tomorrow, but it will take until Wed afternoon to clear out the moisture.  We see a decent afternoon on Wed region wide, with temps rebounding into the 60s; a tad warmer & sunny Thu May 15, but around the Puget Sound, a band of cloudiness will move onshore with a chance for a shower; south and east of that area should remain dry & mild Thu into Fri to wrap up the week.  

The coming weekend.  Across the entire PNW, clouds and precip will increase on Sat May 17.  Cooler temps again, as well, although Sunday could end up as mostly dry & partly cloudy. 

Next week.  The repeating play of cool, damp air masses moving in from the NW will bring even more rain/showers during the week of May 19-23.  For now, models suggest Mon the 19th and Fri the 23rd as the dry, mild days of that week.  Note: it will be a rather chilly system that week, so mountain snowfall above the passes is probable.  Won’t Let Go.

Memorial Day Holiday Weekend - May 24-26.  Model solutions moved up the arrival of more rain/showers during the US holiday to late Saturday (northern WA/BC) instead of on Memorial Day itself;  Sunday is trending wet, however models hold most of the precip to the north of Portland (quite wet along the western slopes of the northern Cascades — if models verify, hikers/campers beware).  All that said, we do know model charts often change, so maybe all will be fine the holiday weekend.

We do see the potential for an extended DRY PERIOD, with seasonally warm temps, AFTER the holiday weekend; the final 6 days of May 2025 could be pleasant.  Hopefully.

As the tag line suggests, it looks like much of May will be on the cooler side of Spring, with minor amounts of precipitation.  Mug ready here, how about yours?

First, let’s deal with the periods in May that could possibly present some precip.  Unfortunately, those periods are likely to fall on the weekends.  However, please note that nothing on the charts indicates super-wet weekends, or enough rain to provide a needed "Nature’s watering”.  (At least that is what wx models have been indicating for quite some time.)  Therefore, expect cloudiness to sneak in mainly around the Puget Sound region on Saturday, with a broader shift to clouds & the chance for showers arriving across the entire PNW by Sunday as the Low we have mentioned several times develop along the southern coast of Oregon.  

On Monday May 12, that same Low will slowly move over the NW corner of CA, resulting in clouds & showers extending north into OR, esp southern OR.  Washington state may miss out on the scattered showers, although a few could pop up along the eastern slopes of the Cascades.  By Tue, clearing & cool temps will remain in play around the PNW through the rest of the week (May 13-16).  Periodic westerlies through the Columbia Gorge will keep windsurfers happy, but the wind drag on river barges will ‘burn’ a bit more fuel.

The weekend of May 17,18 should present another chance for cloudiness & precipitation.  Late Fri, a front will begin to move onshore - broadly up & down the PNW coast - and could be strong enough to set off showers region wide, with the heaviest likely over the southern 1/3 of OR, both sides of the mountains.  Models clear things out again on Sunday. the 18th.  Temps will remain a tad cooler than normal for mid-May.

May 19-23 looks dry, mild to start, however, by Wed, charts indicate a cold front (esp chilly for late May!) could move in from coastal BC, for a chilly end to the week.  Not a lot of moisture is modeled, but temperatures - IF the sky clears in your location - could tease a light frost on Fri morning, May 23.  

Holiday Peek:  That chill will NOT mess up the Memorial Day holiday weekend.  A warmer pattern is likely, with High pressure ridging into the PNW ahead of another system developing offshore - threatening some precip late Memorial Day or Tue May 27.

Monday May 5 

Up & Down temperatures for the next couple of weeks, with a shower or two passing by at times.  Let’s take a peek.  

Today, Cinco de Mayo, will be pleasant and a prelude to an exceptional Tuesday May 6.  Yep, tomorrow looks to be the warmest day out of the next several, as High pressure ridges over us sending temps into the upper 70s to lower 80s region wide.  Oregon coastal zones on the 6th could range in the lower 70s - beach day anyone?  By mid-week, a system will clip the NW corner of WA, setting up a chance for a few showers north of approx. Chehalis, with cooler temps; the rest of the PNW should remain dry, although cooler, as noted.  The last two days of this week look warmer (70s) again, but not the 80s like Tue.  

The next chance for cooler temps & showers arrives during the weekend with a stronger Low pressure trough drifting south off the coast — this will usher in some cloudiness & slight chance for a shower or two, mainly north of Longview on Sat; showers possible around western OR on Sunday.  That Low will continue south, keeping the chance for a showers around the PNW through early next week.  Not too windy east of the mountains, but it will get breezy.  Given the SW flow aloft, temps will remain mild with elevated humidity, relative to normal May levels.  

Indication are that by Wed May 14th, temps will rebound a bit under mostly sunny skies.   Dry wx should hold on into the weekend of May 17,18 for most locations expect the far NW corner of WA and southern BC — there a weak system could keep the clouds around, with chance for a shower or two. 

The week of May 19-23 is trending dry & warmer early - temps in the mid-upper 70s in most locations Mon & Tue - then cooling a little late week before the Memorial Holiday weekend. 

As stated, next week is trending mostly dry, esp early on, with warm temperatures by Tue — upper 70s to low 80s probable, region-wide.  Models do hint at a swing back to increasing clouds & a slight chance for light showers over the far NW corner of WA & Vancouver Is.  This is charting as a weak system, only clipping the NW corner of WA & southern BC; therefore, let’s go with this being a cloud event, rather than rain/showers.  Sip.  For the rest of the PNW (and everywhere else after Tue), expect next week to be mostly sunny and mild; temps in the 70s.  

There is a southerly flow component on the charts for overnight Fri May 9, which would suggest elevated humidity in general, chance for east side & Cascade showers/thunderstorm specifically, throughout the weekend of May 10,11.  Gone is the strong wind issue for the eastern basins.  For the weekend of May 10,11 we expect mostly dry, with some showers/thunderstorms east of the Cascades, with increasing chance for rain/showers/thunderstorm across the entire PNW as the week of May 12 gets underway.  This damp, but mild, pattern could last through the entire week, May 12-16.  Soils will likely become too wet to work, and plant disease pressure is likely to elevate, so plan accordingly should that pattern verify.  We’ll know more a week from now.

Reason for the above outlook: a large Low pressure trough offshore - that was modeled to move onshore over southern OR during that weekend - is now charting to remain offshore as it moves farther south, before essentially ‘parking’ just off the northern CA coast for a couple of days.  The implications of this change is for region-wide muggy temps, spotty thunderstorm activity (both sides of the Cascades) and multiple days of measurable precipitation.  That’s the set-up right now.  

We do see a dry weekend for May 17,18.  Warmer.

Looks like only two ’summer-like’ days are on the charts out of the next seven.  Do they fall on a weekend?  ☕️ Mug up for the answer.  

Onshore flow has helped keep a pesky marine cloud deck around, holding down temps this past weekend, and today.  Not bad, just typical PNW April weather.  We have a weak front that will quickly pass over tonight into early Tue, so areas roughly north of Portland can expect a bit of moisture.  Not much, but enough to dampen the ground.  THEN, Wednesday & Thursday this week will be the 2 ’summer-like’ days out of the next several.  Sunshine & warmth, esp over western OR, which could top 80 inland on Thu; upper 70s possible around the Puget Sound, esp the southern portion.  Friday does NOT look too bad, as the next chilly, damp system may hold off arrival until overnight Fri into Sat morning.  Temps on Fri will be down a bit from Thu, but pleasant & a tad muggy, ahead of the cold front. 

The first weekend of May looks on the chilly side, with periodic showers broadly spread around the entire PNW; clearing some on Sunday May 4.  WINDS will pick-up significantly over the eastern basins of the PNW this weekend, with the strongest located over SE OR & potentially Spokane.  Blowing dust could an issue.  California - generally north of Pt Conception - will turn chilly with some rain/showers & possible thunderstorms in the Sierra Nevada range.  

By the time next Mon, May 5 arrives, we should be out of the broad precipitation mode and slowly warming back up into the upper 60s or so in Oregon; however, an onshore flow is likely to bring a return to the pesky marine cloud deck inland, west of the Cascades.  We do see a weak trough clipping Puget Sound area late Tue through Thu, so mostly cloudy with a chance showers is our ‘call’ for now.  That same trough may hold together enough to bring on clouds and a widely scattered showers over western OR on Thu May 8, as well.  Friday May 9 is trending warmer, with plenty of sunshine in the afternoon.  

The weekend of May 10,11 is looking dry, with partly cloudy conditions under an onshore flow.  Sounds familiar, right?

NOTE:  we do see a possible shift of the Pacific High farther to the NW by May 14 or 15, which, if verified, would usher in warm weather for the second half of May — mid-80s to lower 90s in western OR; warm over the Sound, too.  We’ll see.