It is possible because of the heat island effect of the Portland Metro area. Plus, the east wind in PDX keeps the temperature up at night and is more forceful here than down the valley.

Although the average frost dates differ by a month, the average low per day difference is not enormous, and the average highs per day should be similar.

You wouldn't need to have moved as far away as Salem to see this frost date shift; Aurora or Wilsonville should be closer to Salem's averages than Portland's.

By growing time, are you concerned mostly with a vegetable garden?

The East Wind keeps the temperature up at night? Ummmmm .... I recall freeeeezing East Winds. (Notice the capitalization, as I am convinced the East Wind is animate). I was happy enough to get away from the East Wind and the traffic, though not necessarily happy to leave civilization behind.

Vegetable gardning, yes. I want to make the most of my vegetable gardening. My landscaping plants can wait until it's safe; vegetables are time sensitive.

Rain2Fall

I visit Canby regularly and on many occasions over the decades, I scraped frost off the windshield to start the return trip and arrived home to at least 40-degree temperatures.

Overnight temperatures in an east-windy Portland will always remain significantly higher than when it is calm. A windy winter day may have a hi/lo of 38/28. The same calm day would be 42/22. You are recalling the wind chill rather than the absolute temperature.

Keep in mind that much agricultural business is centered around Salem, the Oregon Garden in Silverton is much frostier than Portland, and there are many successful vegetable gardens around. Perhaps earlier indoor seed-starting, cold frames or other covers, and neighbor's advice is in order.

I wouldn't wager on the frost dates you found. If you search the internet you find it varies by a month.

It also depends on what micro-climate you may living in. We're on the west side of Wilsonville and our little area is always warmer than Portland in the summer and colder in the winter.

I can usually have some veges planted the first week of May.

I'm right in Salem, right on the bottom of the valley. I was re-reading my square garden book to get my thoughts going again, and calculated from last frost backwards, to see that Peas should be started in April, and tomatoes not planted out until June. I'm used to planting peas out in February, even sometimes January, and using Memorial Day as my marker to transplant out tomatoes, eggplants, peppers, and broccoli. I've never had to fiddle with frost protection before, and have always had success. This year I do plan to build a cold frame, but that's to propogate hardwood cuttings of landscape shrubs, not to baby my veggies through a too-cool spring.

Do you other valley people think I can still start my seeds in February and transplant out on Memorial Day?

Rain2Fall

You would need input from someone living in Salem, but I have to say that I was in Corvallis once and the vegetables there were far in advance of mine near Portland, which leads me to believe there is more summer heat which might make up for a shorter growing season. Also I extend my seasons by starting plants early and using tunnel covers to keep them warm earlier outdoors.

Rain2Fall may have an easier time in Salem than in Portland with vegetables. There are many days in spring where partial infiltration of marine air comes up the Columbia and covers Portland much thicker than Salem; that means Salem is sunny by 10AM and Portland by 2PM. This is the case right up to July 4th when marine air generally leaves us alone.

Another east wind example: The low temperature early Monday morning was 34 in Salem, 47 at my place in Portland. But my place felt colder, I'm sure.

I hope you guys are right. Come to think of it, the mid-valley is usually warmer. The ice storms don't hit us here so bad, and I sure don't miss that cold East Wind.

There's a lady two blocks over who has a garden. I'll go introduce myself. I'm going to plan on my usual and accustomed seed starting and transplanting dates, but I'll have some kind of protection ready in case there's a late frost.

It's raining! I love our rain. And the cats have come back inside. :-)

Rain2Fall

Record lows drop considerably as you go down the valley, probably from cold air moving down from the north and then getting boxed in by the mountains. Salem and Springfield-Eugene have some amazingly low all-time lows. For the longest and mildest possible season you would have been much better off on a sunny low-elevation hillside near Portland, with shrubs around the plot to cut the wind, than anywhere on the valley floor.

Sadly, bboy, I think I'm stuck. I bought this place to live while I went to school. Now I'm unemployed and don't stand a chance of being able to sell this place. Can't get unemployment compensation, and you know what happened to my "investments."

Just making the best of a bad situation--being out of work gives me lots of time to fix up the yard and garden. If I can figure out how to build a cold frame I can propogate and start transplants early and get a LOT of food. Plus, I LOVE to garden!

Yes, a hillside place in Hillsdale or Multnomah would have been idea. Oh well.

Have you ever heard of minus zero lows in Salem? Do I recall correctly a few minus zero's in Portland in the 60's?

Rain2Fall

Go to http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?or7500 and click on "Daily Summary Stats". That will give you all the records and averages for Salem (airport). (Airports are often colder than most people's gardens, depending on where you live.) You can also get information about first/last frost probabilities.

Great link! I'm confused with the probability graph -- does it mean that on June 1st, there's a 90% probability of having temperatures under 36 F? That doesn't make sense. Can you help me out?

Rain2Fall

There's a 20% chance of experiencing a temperature below 36F after June 1st. A 10% chance of going below 32F after May 15. A 40% chance of going below 32F after May 1. etc. Looks like your average date of last frost is about April 25 and you're pretty much safe after May 15, if you live at the airport. Memorial Day ought to be a good planting time for a lot of summer veggies since the soil will be warmer then anyhow.

During the cold snap of 1989 or 1990, Salem got down to -10, the coldest at my Portland place was +10 during this time.

The only sub-zero Portland dates are as follows:

Thanks for the extra posts and the explanation, Larry Gene. You must be the weatherman! I'm feeling a little better about it now. I'll plan on Memorial Day for transplants, and start seed accordingly.

Rain2Fall

I lived in Beaverton for 14 years and now live in Canby for the last 5 years. About half-way between Portland and Salem. I was glad to be moving (a little bit) away from those east winds. The east winds are are always responsible for the coldest of the cold winter weather. Unfortunately, if they persist they can fill up the whole Willamette valley.
Unless your were living in downtown Portland, I sincerely doubt that you'll have an extra month of spring frosts, although frost pockets can be a problem. I remember frosts in Beaverton in late April. But I wasn't paying as much attention then as I do now. In the last 5 years in Canby I've seen frosts as late as May 2nd. When the skies clear and the air is still in April, it *will* freeze here, likely in areas surrounding Portland too, but not in the cement jungle.
I truly doubt you will have frost anytime after the first week of May in Salem.