So here’s the background. I was talking to my sister about growing zones, and we had an argument over whether or not Portland (OR) should be Zone 9. (It actually is 8b/9a-- the disagreement was over whether or not 9b SHOULD be included.) To qualify for full zone 9, the minimum winter temperature cannot dip under 20 degrees F. I argued that I couldn’t even remember the last time Portland got below 20 degrees; even when we’ve had a couple of days of snow, it just doesn’t get that cold. My sister insisted that the last time it happened wasn’t that long ago.
The way to settle this argument would obviously be to see records of minimum temperatures for our area over the past several years. But the problem is that I can’t figure out a way to do this. It seems like it should be pretty straightforward to see a chart of minimum (and maximum) temperatures by year in major cities, but I haven’t had any luck with finding this. Does anyone know where this kind of information might be? Thanks in advance…
Daytime highs and lows for Portland, OR for every day since 1940. (I happened to know that most cities’ Wikipedia pages have a table of climate data, including extremes, and followed the citation links.) TX stands for the maximum temperatures, TN stands for the minimum temperatures.
It looks like there was a spell of 3–4 nights in December 2013 that got down below 20°F, including one overnight low of 12°F. This may be what your sister is thinking of.
I visited my niece and her husband at Christmas - was it 1992, I think? Give or take a year. Possibly 1991. They had a backyard pool and her husband and I were holding onto the diving board and jumping on the ice on the pool. That was seriously thick ice. It must have been cold for a while, so surprising if it hadn’t been pretty cold. Mind you they lived just south of where I5 turns south after the city, up the hill a ways a few hundred feet higher I assume from downtown Portland.
Which brings up another issue. Downtown <big city of choice> is probably a bad place to be measuring climate, unless that is where you plan to plant your shrubbery.
Or toss a spare sheet over the top (used to be newspaper, but who has those around any more). You might lose the tips on some branches, but especially if it’s not windy, the plant will survive.
Anyway, yes, a lot of the plants would be pretty much in central PDX.