I have been debating several different weather topics I could discuss in this issue. Should we move on to the new weather school topic of atmospheric stability? How about how to measure snowfall? With the nice weather we have been having lately I just couldn’t make myself write about snow – we’ll tackle that topic next issue! There have also been some rumblings from the global warming/cooling debate that we could look at, but I think I will leave that for a time when I feel like a good argument.
It seems that my mind was made up for me when I received an e-mail asking about Indian Summer, just what is it and are we experiencing it right now? While I did explore this topic a few years ago, I don’t think it would do any harm to take another look at it.
When I did some research on the topic of Indian Summer the most common response that I found is that Indian Summer is a period of warm weather that occurs sometime in late September or October. After researching the details of Indian Summer I found that this description is actually not that bad, but that is the problem with the term Indian Summer. There just does not seem to be a set definition. The definition of Indian Summer appears to be set by the geographical region rather than by a defi-nite set of criteria, with different areas of North America defining Indian Summer a little bit differently.
For the area of the Great Plains and the Prairies of Canada, Indian Summer is defined by a particular set of criteria – this should help us to determine when it is occurring. It is generally accepted that for Indian Summer to occur the following conditions must be met:
1. There needs to have been a hard or killing frost.
2. Mostly clear skies (or perhaps local fog at night).
3. No precipitation.
4. Light winds and generally calm nights.
5. Daytime maximum temperatures greater than 18C.
6. Nighttime minimum temperatures staying above freezing.
7. Condition lasting for at least three days. – Keith C. Heidorn
Now, it is pretty late in the year for us to consider this to be Indian Summer, but we did hit nearly all the criteria as set out by Heidorn. We missed out hitting point No. 5. While it has been relatively warm for this time of the year, it definitely didn’t get warmer than 18C, at least that I could see. Also, nighttime temperatures did drop below freezing for most places. Still it came close. In September, we saw summer continue so we never did see a killing frost. Then in October the cold weather arrived along with what seemed to be endless clouds, and that all but dampened any chance of seeing an Indian Summer.
If we look at the origins of the term Indian Summer we don’t find criteria laid out, but rather descriptions of a more poetic nature. The earliest reference found in the literature dates back to January 17, 1778, when St. John de Crevcouer wrote in a letter:
“Sometimes the rain is followed by an interval of calm and warmth which is called the Indian Summer; its characteristics are a tranquil atmosphere and general smokiness. Up to this epoch, the approaches of winter are doubtful; it arrives about the middle of November, although snows and brief freezes often occur long before that date.”
The fact that de Crevcouer stated that this was called Indian Summer, suggests that this term must have been in use before this time. I think his description beats the criteria set out by Heidorn hands down. So I say, what the heck, let’s call it Indian Summer, let’s get out and enjoy it, because as we all know, it won’t be long until we’ll be seeing the cold and snow move in as Old Man Winter starts his long yearly visit. To wrap it up this issue, here is another Indian Summer quote that sums this type of weather up nicely.
“It is only here in large portions of Canada that wondrous second wind, the Indian Summer, attains its amplitude and heavenly perfection – the temperatures, the sunny haze; the mellow, rich, delicate, almost flavoured air: Enough to live – enough to merely be.”
– Walt Whitman, Walt Whitman’s Diary in Canada, 1904.