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When EC first posted the 1981-2010 normals back in 2013 (or was it 2012?), they posted them as a single document for download. Later, they posted the data online, but you can't sort online like you can if you would have downloaded the the single database file like I did. The online version did not include places like the two Iskut stations and most of the others along the 750 km of highway 37 because they had less than 15 years of data (this is because most of the rural and remote weather stations have closed in Canada some 20 years ago). Here is Dease Lake which is close to Iskut, but has warmer nights, and thus a longer frost-free period. Click on the frost-free data (after clicking on the "normals data", and it will tell you that Dease Lake has 51 days of frost-free.
I messed up slightly on the Dease Lake number. The average is 58, not 51. 51 days is the 50% mark were the probability is 50% that the frost-free period will be less than or equal to.
Oh, and Eureka, Nunavut (the coldest place in Canada) has a frost free period of 48 days. This is much longer than you'd find in Iskut, where I grew up in the Chilcotin, or even the higher elevations around Kelowna (eg. McCulloch Lake).
Similarly, the coldest place in BC, Fort Nelson, has a frost-free period of 117 days, which is longer than most of British Columbia.
Longest: Most of Central and South Florida has a 365 day frost-free period, with most of the Keys never having experienced a freeze.
Shortest: Crestview (March 26-Nov 8) 228 days
Normal frost free period is early May to late October here, though some years it is April to November.
Frosts have been recorded in the UK every month (last August had a few), the only place that can go a year without is the Scilly Isles.
Actually other locations on the south coast, as well as central London have had totally frost free years. Southsea, Portland & Penzance for example have all had frost free years...
Here in Malta it is totally frost free, with the record low being 1.2C.
The most frost free area of Portugal is precisely the Capital, because river Tejo estuary (20km wide, east of Lisbon), attenuates cold fronts, last time Lisbon(city, area of 81Km^2) had negative temperatures was more than 6 years ago, in January 9th 2009
It averages 0.0 for some 30 year periods, all time record is -1.2ºC.
IPMA - 012
As you can see here, one of the two official stations of the city didn't had a single frost between 1971 and 2000.
I was just looking at Kelowna. At the lowest elevations like the airport, the frost-free period is about 140 days long. The higher elevations has a frost-free period of over 200 days, but as you climb out of the city to the top of the valley some 3000+ feet above sea level the frost-free days drop significantly. At 4000 ft (1200m) the frost free is already down to below that of Eureka, Nunavut.
This would explain why the vineyards and orchards are mostly planted on benches above the valley floor, but not too high up the hillsides.
Longest: March 9-December 10--Cape Hatteras, NC
Shortest: May 1-October 13--Boone, NC
For the U.S., LA Mex already mentioned the most frost free places.
The place with the shortest frost free period outside of Alaska is probably Leadville, CO with an average frost free period from July 7 to August 16.
Longest in Norway, and this is avg last overnight frost in spring - avg first day overnight frost in autumn/winter:
March 19 - December 5 at Slåtterøy (59 54 N), that's 260 days.
In my region, average:
April 4 - November 20 at Sula (63 51 N)
Shortest in the country, populated place:
Siccajavri (386 m) in Kautokeino: June 17 - August 8 (but can have frost in July)
Last edited by Jakobsli; 01-28-2015 at 03:43 PM..
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