Average last frost date moved up?

[Cameron K.]

Every where I look now the average last frost date in Nashville is April 6th or 5th, however I thought it once was April 15th. Anybody else notice that?

[toastido]

Every where I look now the average last frost date in Nashville is April 6th or 5th, however I thought it once was April 15th. Anybody else notice that?

April 15th frost is from the rapid expansion of wallets from people paying their taxes at the last minute.   (Little physics joke) 

[Thundersnow]

Every where I look now the average last frost date in Nashville is April 6th or 5th, however I thought it once was April 15th. Anybody else notice that?

The folklore advice for planting gardens was always after April 15th, in order to escape the greatest risk of late season frost.  Maybe that's what you're thinking of.

With April 5th only being the average last frost date, you have to figure that half the years would see a last frost date a little after that date.  You wouldn't want to risk planting on the "average" last frost date with that in mind.  That's probably what the extra 10 days are for, so that frost is less likely.

[Thundersnow]

Also, I think there is a last "freeze" date and a last "frost" date, which I believe may be a bit different.  Frosts can continue to happen a few times after the last bonafide "freeze."

[Coach B]

Be very careful if using Nashville dates for anything.  I came across the freeze dates for various middle Tennessee locations in a UT extention publication last year.  They are highly variable, with Nashville being earlier than anywhere else.  I assume because of the UHI effect.

[Cameron K.]

Yeah okay. I guess the 15th is the supposed average last frost, but even still I'd wait a little bit after the 15th let alone 6th before planting. And to correct myself it's freeze date that the records I was refering to show. A freeze is when temperatures fall below 32°F and a frost is when you see frost on the ground which can, as we know, occur above freezing.  http://www.srh.noaa.gov/ohx/?n=otherrecords

[Thundersnow]

I usually plant stuff around or after April 20 or so... by May 1st at the latest.

That makes sense about the average last freeze being on April 5th and the average last frost being on April 15th.  I think the record latest freeze in Nashville was recorded on something like April 25th, as I recall.