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A 37C air temp with a RH of 60% would produce a heat index of 51C. Yeah that would be a little humid
Yeah, as I said, I was reflecting to the average conditions here. Finland has recorded above 37C once (37.2C), and my city has an annual humidity of 80%, so those conditions would be spectacular. When that national high temp was recorded the DP was 10.5C and the 24h relative humidity 51%.
Here in Southern California, 95+ temperatures means humidity is usually less than 20 percent, sometimes lower than 5 percent! So yes, I consider 99 F with 32 percent humidity to be on the humid side.
Yeah, as I said, I was reflecting to the average conditions here. Finland has recorded above 37C once (37.2C), and my city has an annual humidity of 80%, so those conditions would be spectacular. When that national high temp was recorded the DP was 10.5C and the 24h relative humidity 51%.
If the dew point was 10.5C when the air temps was 37.2C the heat index would be 36C Heat Index Calculation
Here is a comparison of average morning and afternoon RH levels for Chicago(ORD) and three NYC stations. On an average afternoon, at ORD, the afternoon heat index is about 31C in July. Which is 2C higher than the air temp. NYC is slightly less humid.
If the dew point was 10.5C when the air temps was 37.2C the heat index would be 36C Heat Index Calculation
Here is a comparison of average morning and afternoon RH levels for Chicago(ORD) and three NYC stations. On an average afternoon, at ORD, the afternoon heat index is about 31C in July. Which is 2C higher than the air temp. NYC is slightly less humid.
As you said yourself, European heat is mostly dry, and my example reinforce that point. When we recorded the highest temp this summer (32.6C), the DP was 17C, giving a heat index of 33C, but a couple of hours earlier the heat index was 31C at a temp of "only" 29.4C (19.4C DP), so the higher the temp went, the lower the RH fell.
Our highest DP was 20.5C this summer, but it occured early morning when the temp was merely 21C.
As you said yourself, European heat is mostly dry, and my example reinforce that point. When we recorded the highest temp this summer (32.6C), the DP was 17C, giving a heat index of 33C, but a couple of hours earlier the heat index was 31C at a temp of "only" 29.4C (19.4C DP), so the higher the temp went, the lower the RH fell.
Our highest DP was 20.5C this summer, but it occured early morning when the temp was merely 21C.
Correct, European heat is mostly a dry variety aside for the coastal Med as countless discussions on this board have shown.
Unlike the US where dew points can be ridiculously high a thousand+ miles away from any large body of water.
Like this example from July 2011 showing heat indecies in Iowa at 129F/54C and North Dakota at 122F/50C
From that July, my suburb it felt like 46C at 10:15AM
and the very next day the heat index was 41C before 9AM and 48C at 11:15AM
I would say its slightly humid yes. If it would ever reach 37°C here (hasn't yet officially), a humidity of 20-25% might be more typical here in my opinion, maybe even below 20%.
I just didn't exactly get what you meant by, "pretty good for Sydney during a heat wave"? The humidity was higher than you expected I guess?
Yes. I see the periods of heat in Sydney are usually extremely dry, so to occur with a dew point of 18C is somewhat remarkable for your climate. In fact, even the notorious New Orleans saw 36% humidity when it was 37C:
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