Not Much Rain & A Look Ahead Into May

9pm Sunday…

Well, it rained a bit yesterday, but officially nothing in Portland today. Showers were widely scattered and mainly concentrated over the Coast Range and Cascades. Saturday’s showers showed up and were about what I expected, but not today.

Officially nothing measurable fell in Portland, which means it’s still the driest April on record with just five days left this month. I think there’s a very good chance it’ll remain the driest April we’ve seen…more on that below


A cool upper-level low (pool of cold air overhead) is sitting along the West Coast this evening. It’s going to stick around for one more day

But that trough leaves late tomorrow as strong and very warm high pressure builds in the upper atmosphere. By Thursday its hot anywhere south of southern Oregon and quite warm here. We could be close to 80 again Thursday

The ridge flattens for the first weekend of May, which may (or may not) lead to some decent showers

But there doesn’t appear to be another cold trough headed our way for at least 10 days! By Wednesday the 5th of May, weak ridging is overhead again

I’m only showing you one operational model, the ECMWF, but others are similar with upper level heights running higher than average the next 10 days…which takes us into the first week of May. It’s pretty clear that the much anticipated turn towards a wet spell is looking a bit weak. The GFS, ECMWF, & GEM models barely produce 1″ of rain in the lowlands of western Oregon & southwest Washington the next 10 days. And these numbers seem “irrationally exuberant” when compared with the upper-level maps.

To summarize:

  1. This record dry spring will continue into the first week of May.
  2. You will need to continue watering this week, since I don’t see any significant rain (0.25″ or more) until at least Friday evening
  3. It’s possible we still don’t get a soaking next weekend either, but we don’t know yet.
  4. We have three guaranteed dry days Tuesday through Thursday as the ridge builds overhead


I figured we could get at least 1/2″ of rain this weekend through tomorrow plus a bit more later next week. Not typically a tough feat in April. That’s why I was poo-pooing the idea of seeing our driest April on record. But as of tonight it’s looking quite likely once the clock strikes midnight this Friday. The last 7 years…

Notice last year was also in the top 5 driest Aprils… If we get more than .27″ rain before midnight Friday, it WON’T be the driest April on record at PDX. That may happen

Of course something we have been talking about for the past few weeks has been the record dry spring. It’s amazing to think we’ve seen less than 2″ rain in all of March and April! This year just 1.81″ at PDX so far. These records go back to 1940. I also checked the downtown location (records back to around 1880); there appear to be only two other springs so dry, 1885 & 1926. Its the driest spring in Salem since 1926 as well…so far

This is the 2nd spring with very dry March-April conditions. 2017 was a soaker eh?


First, there’s no reason to freak out (yet) over the lack of spring rain.

IF we get deep into May with these conditions, I’ll start getting concerned. If the dry pattern continues into early-mid June then we have a serious problem. That’s only six weeks away.

We already know that we need at least normal rain from this point forward to fill reservoirs like Detroit and Green Peter. And we also know drought conditions continue to creep north through Oregon.

Lack of mountain snow and warm temperatures have caused a faster-than-normal melt in the Cascades. The snow melt season had been delayed due to a chilly March, but now snowpack is below average in most of Oregon

Does a dry March+April mean we’re headed for a serious drought? Possibly, I did a little bit of research this evening. I looked at the ten driest springs (up to this point) and then looked forward into May and June to see what happened. Here you go:

Yep, it was a divided verdict. In 2-3 years we saw a soaking in May, or June, or a combo of both in 4 of those years. But in 6 of those years, drier than normal conditions continued as we headed into early summer (June). It is interesting that only one May saw less than 1″ of rain. That shows you how unusual it is to have a sub 1″ rain month in spring in Portland. That’s what we’re seeing right now.

The following summers? I didn’t check rain since we don’t get much in July/August anyway, but I did check temperatures. Only 1 of the 10 summers could be considered a “cool” one. All the rest were average or hot. Does that mean we will see a 9th consecutive warm/hot summer? We don’t know, but this would imply a dry spring can lead to at least a normal/warm summer.

So…there’s a decent chance we continue with a dry-ish spring, but there’s no reason it can’t still turn around.

For now, keep watering! Chief Meteorologist Mark Nelsen

50 Responses to Not Much Rain & A Look Ahead Into May

  1. tim says:

    Looks like a good soaker next weekend.

  2. Roland Derksen says:

    I ended up with 1.85 inches in total for April- which is well below normal for my location in BC, and 72% of that came over the last 7 days, with the heaviest day of precipitation for the month on the 30th at 0.58 inches.

  3. 5OClockCharlie says:

    Some light but steady showers right now in South Metro. Smells like the warm rains we get sometimes in the middle of summer, very fresh and comfortable temperatures. Records be damned, here’s hoping we squeeze .25″ out of this pitiful system 🍺

  4. Paul D says:

    Looks like rain today is a bust. Bummer! (not surprised)

  5. Joshua Lake Oswego says:

    Our rainy, cool, and cloudy days sure aren’t what they used to be. Partly sunny, warmer than average, and dry as a bone today.

    • Anonymous says:


    • 5OClockCharlie says:

      Evidently the models have been unreliable for some time. One day there’s a system coming, the next it’s gone completely only to come back again the following day hundreds of miles away from its previous location. Even 24 hours in, they’re still having trouble. This is bonkers

    • Tanis Leach says:

      Part of at least the lack of rain can be attributed to cycles. Most of the time, Portland appears to have below average years clustered together and above average years in the separate cluster. Near average can go into either cluster. This is best shown in a 10 year stretch of below normal rainfall from the mid 80s to the mid 90s (don’t remember if 93-94 was the last year or 94-95).

      I can’t scientifically prove this, I’m just looking at the water year data.

    • EY (Oak Grove) says:

      A brief period of light rain can be expected early this morning,
      through 6 AM.

      Wanted to make sure this announcement is saved for posterity reasons.

    • pappoose in scappoose says:

      Yes, one for the books for sure.

  6. Joshua Lake Oswego says:

    The GFS operational gives us less than .10” through the middle of May. The always overly-optimistic ensembles aren’t a whole lot better.

    At this point, it seems like we need a parting of the Red Sea type of miracle to get a widespread soaking. 2021 could be the year with a 6 or 7 month summer.

    I’m not referring to temperature, W7. I’m referring to the consistent ridging, lack of precipitation, and abundance of sunshine.

    • tim says:

      Looks like our May heat wave by mid month too usually we se a stretch of hot weather by that time.

      • Joshua Lake Oswego says:

        The GFS has a death ridge directly over us in mid-May. I won’t put too much stock in that right now, but there is certainly no indication of a wet period any time in the foreseeable future.

  7. tim says:

    Keep the rain to south into Oregon were they need it everything here in western Washington is a wet sponge.

  8. Roland Derksen says:

    Some light rain expected here this afternoon, and a somewhat heavier amount to come overnight on Thursday/Friday. It’ll be a drier than normal April, but like Mark, I won’t get too excited until I see how May goes. I recall the spring of 1998- dry and warm, except for 3 days of heavy rain in late May.

  9. 5OClockCharlie says:

    Hurrah! Middle of next week the Euro is predicting a low coming straight at us. I think even with a slight change in trajectory, it’ll be close enough to where we get some decent measurable rain!

    • Zach says:

      Hopefully, but at this point my expectations are low. There seems to be something weird going on that has been causing all these systems to lose their energy a few days before landfall…

      • 5OClockCharlie says:

        This is funny. You and I seem to have opposing opinions each time where previously you were more optimistic and I wasn’t, now apparently it’s reversed hahaha

        I’ve offered an explanation for those low-energy systems before. It’s because the vast majority of those systems were landing in B.C. or Alaska and we got the left-overs. Well those left-overs are really weak and even minor shifts in the storm trajectory up north or pressure changes near us causes huge disparity in what’s predicted to hit.

        In next week’s case we’ve got a low heading directly – dead center – at us this time. If it moves slightly north we still get moisture. If it moves slightly south we still get moisture.

        • 5OClockCharlie says:

          I guess I should’ve added a disclaimer that IF the low actually hits shore somewhere, which I guess as the other folks pointed out, is unlikely

        • Mr T says:

          Not as long as they (keep) blasting our skies to death we’ll be lucky to squeeze out more then sprinkles.. 😦 As soon as our forests and towns all burn up we will get copious amounts of moisture from fires to floods for us whom remain.

    • Joshua Lake Oswego says:

      Yea, but the operation run has more precipitation than any member of the ensembles. No other model support. Let’s keep our expectations really low.

    • Tanis Leach says:

      I want to believe it will happen, but ensambles are a lot more pessimistic. By next Thursday, the 10-90% ensamble range is .27-1.22 inches (average .7 inch), The main run is showing 1.75 inches by that point, and 1.4 inches in the previous 36 hours. I don’t like those odds. If I had to gamble, we have a 50/50 shot of exceeding .5 inches (since due to current patterns, the actual precipitation has been leaning closer to the 10% rather than 90% like 16-17

      • 5OClockCharlie says:

        There is an area of really high pressure that’s stubbornly sticking around fart east of northern California which I suppose could alter those plans quite a bit, but otherwise i’m not sure why the ensembles aren’t falling in line. As of now the 12z GFS is showing a similar setup as the 00Z Euro.

        50/50 of exceeding .5 seems pretty good compared to what we’ve seen so far 😀

        • Joshua Lake Oswego says:

          And… poof, it’s gone in the 12z Euro.

        • Tanis Leach says:

          50/50 of exceeding .5 inches does seem good, until you realize that its an 8 day forecast. Also, is anyone else getting an issue where you can’t see your reply when your typing it?

        • 5OClockCharlie says:

          I see my mistake now, so I apologize for the misplaced optimism. I failed to account for that rapidly intensifying high pressure from the north pole which appears to be causing a blocking effect. That low just stalls far out past our coast until it dies which is probably why the ensembles didn’t like it

  10. Weatherdan says:

    I saw an educational film in our grade school auditorium when I was in the 4th grade in 1964. It was titled our warming world. They talked about global warming even almost 70 years ago. We were warned but ignored it. Now we are starting to pay the price. Peace.

    • Andy says:

      I remember in the 70’s they talked about an ice age…they also said we would be out of oil in 20 years…currently world temperatures are running about average. I wouldn’t panic yet.

      • Anonymous says:

        What you’re referring to is called “Peak Oil” and it was the prediction of a single person and it was trending towards frighteningly accurate for many years.

        You can read more about it here:

        “Hubbert’s original prediction that US peak oil would occur in about 1970 appeared accurate for a time, as US average annual production peaked in 1970 at 9.6 million barrels per day and mostly declined for more than three decades after.[20] However, the use of hydraulic fracturing and horizontal drilling caused US production to rebound starting around 2005.[21] In addition, Hubbert’s original predictions for world peak oil production proved premature.[10] The rate of discovery of new petroleum deposits peaked worldwide during the 1960s and has not approached these levels since.[22]”

        • Andy says:

          We haven’t ran out of oil that was my point…people in science and politics make a lot of prediction’s and time will tell who is correct. Climate is changing for many reasons…if you look at weather data for the NW…we have a very small window in years compared to the past when no records were kept.

  11. W7ENK says:

    Back home from a 10-day road trip through Idaho, Utah, Wyoming, Colorado; down through Southern Utah, back up thru Idaho and home again. Got snowed on almost every single day from the day we left home to the day we left Denver. Woke up to 5-6 inches of snow last Tuesday morning, but ended the day at almost 70 degrees in Moab. The Desert SW is absolutely beautiful this time of year, filled with so much color. Covered a lot of ground and saw a whole bunch of really amazing and beautiful places/things.

  12. Jason Hougak says:

    Climate Prediction Center maps shows the entire western us from the Rockies under drought conditions. Only the Willamette Valley north through western Washington isn’t listed. Not a good situation heading into summer.

    • Jake in Gresham says:

      We’re not there just yet because Mt. Hood and the other upper elevation parts of the Cascades.

      I went up there Sunday to Timberline and it was snowing; piled along the road as high as semi-trucks in places. Lots of people snowboarding and skiing.

      • Jake in Gresham says:

        If none of you have not been up there, go now. The roads are clear and wet all the way up there and the mountain is majestic as it gets for Spring time shrouded in fog and precipitation with blue skies peaking.

  13. Joshua Lake Oswego says:

    Prepare yourselves for a couple of hours of drizzle later this week. Any chance of actual rain is gone. Not like any of us actually thought we would get more than a few hundredths of an inch anyway.

  14. Roland Derksen says:

    Well, all I know is I won’t have a record dry April. As far as May goes, i doubt I’ll ever get to see a May as dry as the one in 2018.

  15. 5OClockCharlie says:

    Once again I’m lowering my expectations for Friday night rain. I’m sure Seattle will get some decent moisture out of it, but .25″ for us is asking a lot from the remnant of a dead system.

    That said, this really stinks and I’m very nervous about late summer. I hope by some miracle we get a couple of soaker days in July

  16. Jason Hougak says:

    The precipitation that Portland gets is peanuts compared to the higher terrain. The super low humidity, warm temperatures, and lack of precipitation is not a scenario we need following last September. We are in a bad situation already no denying that!

  17. Paul D says:

    Keep watering? When did you tell us to start watering? I must have missed it.

    Watering in April – very bad sign….

  18. Greg Carich says:

    “There’s no reason that it can’t still turn around.”

    And there’s no reason that it won’t stay the same.

    6/10 says drought. And heat, to boot.

    Watch out, folks.

    • tim says:

      I fear a region wide firestorm in the not to far distance, even tho WA has been very wet this year that doesn’t mean we won’t burn either, let’s hope not.

  19. Oliver Watson says:

    I really love and respect Mark Nelson. He always presents the facts and has lots of data to back up his thoughts. That’s what we need to look at, not media hype or political bias. My only fear is that going forward is that past data can only help so far in predicting the future because it really seems our climate is being affected by things which we don’t fully or even partially understand

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