May 10, 2012

Summer in May

It is a climatological oddity of Northwest meteorology that we often get a period of very warm, dry weather sometime in the second or third week of May, followed by a retreat into the dismal June Gloom.  Well folks, we are about to have the heat wave--one that will bring near 80F temps to Seattle, 85F to Portland, and near 90F in Medford.  The latest National Weather Service forecast for Seattle says it all:

The interesting thing is that for the last few days we have had fairly cold air over us, and with relatively clear skies and good radiational cooling to space, temperatures have fallen well below freezing in the cooler spots.  For example, it got down to 19F in Redmond, Oregon early Thursday morning---here are the minimum temps that morning...plenty of 20s and sever teens!
The was so cold aloft that considerable instability was produced as the surface was heated by the strong May sun....producing some impressive cumulus development.  Take a look at the UW cam image at around 7:30 AM and three hours can see the destabilization due to surface heating:

During the next few days you will see progressive warming...lets look at the predictions by the UW WRF model for 5 PM on Friday, Saturday, and Sunday.  The light pinks and whites are in the 70s and higher.  You don't need to be much of a meteorologist to understand what this means....

White hot!   Clearly, the mothers in the NW are particularly deserving this year.  Amazingly, it s our fifth good weekend in a row.  And Monday will be warm as well.  Even your tomato plants will be happy.

Final reminder for those near Portland...I will be talking at OMSI Science Center in Portland at 10 AM, looking into the future of weather prediction.   The lecture is free, although the Oregon Chapter of the American Meteorological Society will be raffling off a fancy weather station and one of my books.   This chapter is one of the biggest and most active in the U.S. and recently they had some highly controversial sessions with both sides of the global warming debate.


  1. Teens in central Oregon, wow. Must be why they don't have fruit trees in that area.

    Apple blossoms are in full bloom. Fortunately we've been receiving winds at night, keeping it around 40.

    Anyway, love these thermal troughs setting up on the westside. We have glorious, calm evenings here in wind country.

  2. LOVIN' IT! I hope we don't regress in June!


    Cliff, I would be interested to hear you take on this article as it relates to one of your recent blog posts.

    Enjoy the weather this weekend!

  4. The tomatoes will love the afternoon but cringe at night. Almost ready to plant my starts. It was a close call Sat am in east Renton area ... 34 at sunrise. I was up during the night misting my hardy kiwi vine's tender growth to save from potential frost. It worked as the heat released by light frost beginning to form was enough to keep it frost free. The car had ice on it. Saved hundreds of mini kiwis! Now please no more perfect radiational cooling nights! I think we are finally safe from frost. Justin

  5. Oh and the other gardening tip: How to protect tomato plants from frost.

    Answer: Don't plant until mid-late May around here.

    Even nights down to 40 will stunt the growth. I've had volunteer plants pop up in early June and overtake the starts planted in May. The best is if you can build a plastic frame to cover them at night. Don't forget to take off during the day. I had a thermometer inside one I had to test yesterday in sun. It was 60F outside and 100F inside the plastic frame / mini greenhouse. Justin

  6. Great forecasting the last few weeks. The nail was hit squarely on the head.

    Yes, about the great sunny weather in May. Even as a ten year old, living in Yakima, I witnessed the hot days in May, and then the cool down in June. Yes, even Yakima was affected. Not so much rain and drizzle, of course, but a cool down. Our family moved to Kirkland in 1964, and I saw that trend continue on this side of the Cascades. It looks as though it is repeating itself, this year.

    Incidently, thanks to your great forecasting, my corn started emerging TODAY. I planted seven days ago. As Territorial Seed states on their corn seed packages: Sowing in cold, wet soil only brings disappointment.

  7. Summer in Monterey CA as well. Only difference is that it is 58deg with a 20 knot NW wind and overcast low stratus and fog.

    Pass the sun screen.....norht

  8. What sides of the global warming debate? The scientists versus the shills for the fossil fuel industries?

    It's all about maintaining the status quo so the fossil fuel industries can keep making profits now at the expense of everyone else later.


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