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Three or more consecutive days with temperatures above 32 C is the commonly used "official" definition here, although I have actually read in an article, a meteorologist was quoted as saying Environment Canada, as an organization, doesn't have a formal definition. Nonetheless the "3 consecutive days above 32C" is the one I see referenced all the time, and cited in news articles, often even with the word "official" actually attached, so that's the one almost everyone who cares about having a definition for a heat wave takes for granted.
Some other parts of Canada, including Quebec, seem to use a lower threshold of 30C rather than 32C.
Yes, the record high low temperature for the UK is something like 23C, so anything above 18C is pretty unusual and even during the hottest months here nights above 18C are virtually unheard of, even if the high temperatures are in the low 30'sC, the low temperature will usually fall back to 15C and below. The highest overnight temperature I can find for Leeds is 19.4C
I know England doesn't get that, it's just odd when many times I don't find these temperatures uncomfortably warm, let alone a safety hazard. Didn't occur to me to take precautions.
Of course in a place like Texas, they find find the Northeast definition of a heat advisory silly. Brownsville, TX reaches heat advisory levels (>105°F heat index) 2/3 summer days. This is the definition of a heat advisory in Texas:
A heat advisory is only issued when the heat index exceeds 105 during the day and 80 at night for two days in a row.
I must say I'm impressed at how the English and French definitions are localized/tailored to fit small-scale regions within the country.
Despite North America's great variation in climates, that level of customization isn't something I have really heard of on this side of the pond.
Quote:
Originally Posted by Rozenn
Apparently these are the threasholds used by Meteo France. Northern France is similar to London, at 18/32C. I find them quite high in SW France, with a 100F+ threshold in Toulouse.
Quote:
Originally Posted by ben86
Since the 2003 heatwave in western Europe which killed so many elderly people the health service in England issues heat warnings when the temperature gets above a certain level, depending on the region. It would be interesting to compare our thresholds with those in other countries (if similar heat warnings exist elsewhere). Here are ours, all in Centigrade:
Region Day Night
London 32 18
South East 31 16
South West 30 15
Eastern 30 15
West Midlands 30 15
East Midlands 30 15
North West 30 15
Yorkshire and Humber 29 15
North East 28 15
I must say I'm impressed at how the English and French definitions are localized/tailored to fit small-scale regions within the country.
Despite North America's great variation in climates, that level of customization isn't something I have really heard of on this side of the pond.
I'm impressed with the French one being as thorough as it is! Odd that there's not, or not as much of the same thing in North America considering the US and Canada are federalised countries and England and France fairly centralised ones.
I'm impressed with the French one being as thorough as it is! Odd that there's not, or not as much of the same thing in North America considering the US and Canada are federalised countries and England and France fairly centralised ones.
Texas' definition is a bit different from the Northeast as I showed
Texas' definition is a bit different from the Northeast as I showed
I know, but I'd have expected the northeast's definition to be broken down a bit more into states/counties considering the climate diversity of a relatively big region compared to the ones in England/France.
I know, but I'd have expected the northeast's definition to be broken down a bit more into states/counties considering the climate diversity of a relatively big region compared to the ones in England/France.
In some ways it might make sense to keep the same levels. Unsafe heat is unsafe not matter where you are. The lower British levels I think are low enough that they are merely uncomfortable to those dislike or are unused to heat, but a 100°F heat index I'd imagine would cause issues for most people.
And nowhere in the Northeast is used to extreme heat; it doesn't happen often that people adjust their habits to constant heat. The biggest difference across the northeast is the cooler, more northern portions are less likely to have any A/C, and central A/C is much less common in the northeast than further south. Boston and NYC set up cooling centers for this reason.
Of course in a place like Texas, they find find the Northeast definition of a heat advisory silly. Brownsville, TX reaches heat advisory levels (>105°F heat index) 2/3 summer days. This is the definition of a heat advisory in Texas:
A heat advisory is only issued when the heat index exceeds 105 during the day and 80 at night for two days in a row.
80 at night! That's only happened once here.
While I can see Texans having different criteria, keep in mind that thresholds for a heat advisory are distinct from experiencing a heat wave, as an advisory implies a certain effect or threat to the population, whereas a heat wave implies a sustained period of "hot" weather (hot of course having varying definitions), regardless of any supposed danger.
Since the 2003 heatwave in western Europe which killed so many elderly people the health service in England issues heat warnings when the temperature gets above a certain level, depending on the region. It would be interesting to compare our thresholds with those in other countries (if similar heat warnings exist elsewhere). Here are ours, all in Centigrade:
Region Day Night
London 32 18
South East 31 16
South West 30 15
Eastern 30 15
West Midlands 30 15
East Midlands 30 15
North West 30 15
Yorkshire and Humber 29 15
North East 28 15
Someone might have mentioned this above... but several years ago I read a met paper on how local weather bureaus in different parts of the world match heat (and cold) weather advisories. The biggest constant is “what is extreme to the local population”....while the level of the above/below normal temp was a side issue (within reason of course). A heat advisory in London or Paris might not raise an eyebrow in Karachi or Orlando.
So I would bet there is a great deal of ‘localism” figured into any regions/cities heat/cold advisories.
I can't find any reference to heatwave definitions through any NZ met services, probably because we don't really have heatwaves. I was working down south a few summers ago, when there were 3 days in a row of 36C/95F, or higher. I made a point of seeing if there were any warnings on radio, tv etc, and there wasn't. Rainfall warning are the big thing here, not heat ones.
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Odd that there's not, or not as much of the same thing in North America considering the US and Canada are federalised countries and England and France fairly centralised ones.
