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[deleted] t1_itza06l wrote

It's possible at your home it hasn't happened yet but the NWS has officially ended the growing season

https://twitter.com/NWSPittsburgh/status/1583086138935214080?t=f47JFQT03MFkcIQpnh1Tgw&s=19

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PolyDipsoManiac t1_itzclpl wrote

I definitely thought it had reached freezing last Thursday, if only briefly.

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James19991 t1_itzcy35 wrote

Technically it didn't at Pittsburgh International, where Pittsburgh's official weather observations are taken, but it's entirely possible it did at your location. You can still have frost too even if it doesn't hit freezing of course.

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Yeuph t1_itziw47 wrote

How does that work? Frost without freezing?

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James19991 t1_itzkvvh wrote

Official temperatures are measured 6 ft above the ground or so, and cold air sinks, so if it's 33 or 34 above the ground, it's totally possible for it to be 32 or 31 at ground level in certain areas.

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LordApocalyptica t1_iu05jdn wrote

Also the heat exchange mechanism of phase change means that at a micro environmental level you can have phenomena like frost happening even if the ambient temp is slightly higher

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KentuckYSnow t1_itzkw4b wrote

Temps at ground level can be a few degrees colder than just a few feet higher and dip below 32, at which point the vapor in the air can freeze.

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babyyodaisamazing98 OP t1_itzks3d wrote

That’s strange. The lowest temp a can find for Pittsburgh was a brief hour long dip to 33. I don’t see anything at 32.

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[deleted] t1_itzldwr wrote

Frost can kill plants off before it goes below 32.

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Elouiseotter t1_itzmjld wrote

It also depends on where the temperature was taken in Pittsburgh. For example Lawrenceville with all the buildings and little open space tends to be hotter than Allegheny Cemetery that is mostly green space.

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booksgamesandstuff t1_iu0d4ov wrote

I’m just a few miles away from the airport and all of my flowers perished from frost the same night last week. I’m in a valley and I’m sure houses at the top of our hill may still have some left. It’s not always a blanket…temperature varies.

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covertchipmunk t1_iu2hlq7 wrote

Microclimate! The one in my yard generally works in my favor. It tends to stay a bit warmer based on landscape features and location. So far my roses, dahlias, zinnias, and cosmos are still going. The plants in a less protected spot have started to die off. Sorry your flowers are done. Time to start planning next year....

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booksgamesandstuff t1_iu2kbp2 wrote

I've had geraniums out in the open in front of my house since early May, and they're still blooming. The only ones left as of now and they really don't compliment the pumpkins out there... ;D

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regulartimer t1_iu2rw9d wrote

My zinnias and cosmos were the last two left. They were still budding, but this past weekend, I put them out of their misery. I figured I’d end their season in a vase, to hang on to the last shred of summer.

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mpp827 t1_iu2i21f wrote

>https://twitter.com/NWSPittsburgh/status/1583086138935214080?t=f47JFQT03MFkcIQpnh1Tgw&s=19

So that means they won't issue frost/freeze warnings anymore?
Good to know that because I have been relying on it for my garden.

Still kicking in the south hills. Picked tons of dahlias this week, again.

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