With the deary and cold conditions here as promised, and the unfortunate snow incident for Northern, Central, and Eastern Ontario today, I thought I would do some research in terms of the impact on the upcoming summer weather.
First off, while snow in May is never out of the question for Northern, Central and Eastern Ontario; it is really not all that common for Ottawa. In the last 50 years, a trace of snow in May (the worst in 1976 with 8.6 cm) in Ottawa has only occurred 17 times. 1967, 1969, then six times in the 70’s (70, 71, 74, 76, 77, 78), four times in the 80’s (83, 84, 86, 89), once in the 90’s (96), twice in the 2000’s (02, 04) and twice in the 2010’s (10, 13). Not counting this year which may end up around 1 cm recorded from the airport (.02 cm last night plus whatever fell today) however my location west of the city (like bigmt’s) was closer to 2 cm. Here is my view this AM:
So what does all this cold blocking pattern maybe mean for the summer? Well in researching the stats, it’s not all that good. Of the 17 years with a trace or more of snow in May; nine or just over half of the summers were mostly below normal in June, July and August (1967, 1969, 1971, 1974, 1976, 1977, 1978, 1986, 2004). Seven years (1970, 1984, 1989, 1996, 2002, 2010, 2013) the following summer months were near normal, with maybe only one month slightly below normal (typically it was June).
However, take comfort, one year, 1983 was actual +1 or +2 degrees above normal for the summer months following a cold May with snow. By the way, for the statistics, I am using the mean (average of the daily High and Low temperatures) for the month.
One thing to note which was interesting; while most May’s with snow finished off the month below normal, six years (1977, 1978, 1986, 1989, 2010, 2013) the average temperature actually finished above normal. However, five of those six years (1977, 1978, 1986, 2010, 2013), June finished off below normal after the warmer May, with only June 1989 coming in near normal. Of those five years, three of them (1977, 1978 and 1986) the cold trend continued for the month July. The absolute worst was 2004, where May, June, July and August all finished off at least 1 degree below normal. That year was dubbed “The year without a summer” in many location across central and eastern North America.
So what does this all mean for this year; well if you where a gambler, you would probably roll the dice for a below normal summer this year. However, there are always surprises with the weather, even when you have past history on your side.
My summer forecast should be coming out in the next week or two.