Everyone says that the average last frost date in Vancouver is March 28 and everyone says that this date comes from Environment Canada. But I have never seen any such date in any EC material. Some years ago Eric directed us to this thread: http://www.botanicalgarden.ubc.ca/fo...ad.php?t=20089 in which he repeated the March 28 date and attached a link to a table, said to be extracted from EC data, for the 37 years 1958-94 I looked at that table today and noticed that for those 37 years the last frost date was after March 28 6 times and on or before then 31 times. Now, I know that "average" can be mode, mean, or median - or I used to have some such vague idea - but this did not seem right to me. So I just took the arithmetic average of the number of days from January 1 to last frost, and found that on that basis the average last frost date is nowhere near March 28. It is March 14, two weeks earlier. Of course that data ended in 1994 but my sense is that the last frost date has if anything become earlier in the last 2 decades since then. So ... does anyone know of the actual source of the widely-repeated March 28 date?
