Heat vs. humidity

[JDgreen227]

We have had maybe 3/4" of rain total in the last six weeks and the heat in mid-Michigan is setting an all time record so far this month. What baffles me is that despite the sunshine and heat and dryness, it still seems really humid outdoors and I am not smart enough to understand why.

Anybody care to advise me? Thanks.

 

[MIKE R]

We are getting warm weather up here at the top end of the I-75 but no where as bad as y'all are getting it. I think that it is dry but humid because the Air at a specific temperature can hold a cetain amount of moisture, as the air gets warmer the more moisture it can hold.

 

[rswyan]

We have had maybe 3/4" of rain total in the last six weeks and the heat in mid-Michigan is setting an all time record so far this month. What baffles me is that despite the sunshine and heat and dryness, it still seems really humid outdoors

Some days it is .... some days it isn't ....

Personally I tolerate "dry" heat with low (relative) humidity much better than I do "wet" heat and high (relative) humidity.

and I am not smart enough to understand why. Anybody care to advise me? Thanks.

Read the sub-section entitled "Comfort" under the section "Significance" at the following link - it explains what humans typically perceive - the rate of body heat transfer - which varies and is affected by humidity (and temp)

Relative humidity

Basically the way I read it, is that because humans use evaporative cooling (which is affected by humidity), if it is abnormally hot, it might seem more humid .... even if it isn't all that humid ....

 

[bcp]

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[JDgreen227]

Guys, it IS really humid....currently 93% !!! Perhaps I didn't phrase the original post properly...just wonder HOW it can be 93% humidity when it is blisteringly hot, dry, and sunny. Seems like the constant heat, as much as 102 degrees yesterday, would make it much drier.

 

[oldnslo]

If you are near bodies of water or areas being irrigated they can act like a steam bath in high heat conditions. The sun causes evaporation from the these water sources which will raise the relative humidity in that area. This is usually more noticeable on calm days.

 

[mostly_gas]

In my neck of the woods, the air circulation around the high and low pressure systems will pump up the moisture of the Gulf of Mexico. If the air mass is stable no thunders storms develop and as a result, no rain

 

[JDgreen227]

If you are near bodies of water or areas being irrigated they can act like a steam bath in high heat conditions. The sun causes evaporation from the these water sources which will raise the relative humidity in that area. This is usually more noticeable on calm days.

A few small lakes 5-10 miles away and no irrigation nearby at all, and the wind we get always comes from the west and there are no lakes in that direction for 15 miles....

 

[dodge man]

The humidty is just in the air, it comes from somewhere else. You will see the humidity drop as the temp rises. Keep an eye on the dew points, that is more of an idicator of how humid it is. Dew points in the upper 70's make it seem real humid, not matter what the temp is.

 

[rswyan]

Guys, it IS really humid....currently 93% !!!

Your post, written around 08:00, is just after a period where it was cooler and dark ...

Perhaps I didn't phrase the original post properly...just wonder HOW it can be 93% humidity when it is blisteringly hot, dry, and sunny.

Check that percentage again at around 15:00 and let us know what it is - if it hasn't rained it will probably be much lower.

Seems like the constant heat, as much as 102 degrees yesterday, would make it much drier.

Actually, heat makes the air more humid initially .... driving moisture into the air by creating water vapor thru evaporation .... which makes stuff other than the air much drier ....

 

[Tenn_Blue]

Being from Florida, I have a good understanding of high humidity! Also watching this with interest, as we are coming up to the Lansing area next week to visit wife's family and do some camping (the camper has a/c so not too concerned, and will STILL be cooler than Florida, or even Tenn lately...)! We are booked into Luddington end of next week, starting to wish we had decided to go to the UP instead......

Another factor in humidity is high level winds - by no means a weatherman, but certain conditions act like putting a big glass bowl over your area that contains the heat and humidity - in Florida, they just call that "summer".....

 

[schoolsout]

Yea, come on down to Charleston, SC if you want to feel humidity!

 

[bigtiller]

I posed the O P's question - rhetorically - and got an invitation to the Arizona desert to cool off.

 

[QueBota]

Charts tell the story, rel humidty tends to drop as temp increases, it reflects the amount of water that is in the atmosphere compared to the maximum amount possible, expressed as a percentage. Dew point would be considered a more accurate gauge of discomfort.

A few days ago we had a dew point temp of 78F, air temp of around 88F. I took some cans of beer from the basement out to the picinic table and the beer cans began to sweat, approx. temp of beer cans was 73F, cans would have sweated until their temp was > the dew point temp. Unusual to watch "warm" cans of beer sweat. Very uncomfortable day to work outside. I drank approx 1 1/2 gallons of water and never took a l#ak.

Under certain circumstances dew point temps can enter the low 80F range and even approach 85F (Gulf Coast states and some midwest areas under unique weather conditons). Almost impossible to work hard under those conditions, just brutal.

Dave

 

[Runner]

Here is a pretty good discussion on relationship of water vapor versus air temperature.

Unit 4: Temperature-Moisture Relationship — Free Online Course Materials ? USU OpenCourseWare