Heat Index Chart and Tips on Heat Safety
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07/15/2024, in our area of Indiana we had 88 degrees with 76% humidity, along with 78 dewpoint & a "Feels like" temp of 100. How does the Dewpoint figure into this equation or was just another stat that the Weather Channel threw into the mix?
If you have the temperature and relative humidity, then you don’t need the dew point to find the heat index. However, you can find calculators for the heat index that just use the temperature and dew point. That’s because the three factors are interrelated.
The dew point is the temperature at which the air would need to be cooled, at constant pressure, so that the relative humidity would be 100%; the dew point can not be higher than the actual temperature. If the temperature were to cool below the dew point, then the water in the air in gas form (vapor) would condense into liquid, such as via rain or fog.
Warmer air can hold more moisture before it becomes saturated. A higher dew point means that there is more moisture in the air than there would be at a lower dew point. A dew point above 75F can feel oppressively muggy.
Relative humidity is the ratio of the amount of moisture present in the air relative to the amount that would be present if the air were completely saturated. It is dependent on dew point and temperature.
Relative humidity at 100% will feel less humid if the dew point temperature is 30F, for example, compared to, say, 60F.
So, it sounds like the weather report gave an extra statistic to help viewers to know the entire picture of how hot and muggy it was outside that day, although all of those stats are related.
In scrutinizing my email, it seemed to be discombobulated. Seems I mentioned in the TX winter "Regs wouldn't allow us to remove our fatigue tops. We often connected an AC unit hose into the B-52 cockpit and get relief."
Hope you figured out it was in the summer heat, not crazy to do so in winter. Sorry and glad I caught it.
Heat and cold extremes are interesting to study and be aware of. I've been a info sucker-upper many years and this is interesting. I've been at both extremes.
For the heat) Joined the Air Force 9/9/1958 and Basic Training at Lackland AFB in San Antonio. It was a hot summer in that region. They had us take salt tablets very often. At 5am in full dress at 5amon the street it was still in the 90's. But that's what was the "protection" at that time. At Shepard AFB in Wichita Falls TX it would "cool off" into the 90's at night. Opened the screenless windows mosquitoes the size of hornets would attack you. There was no AC in either places. Assigned to SAC and in that Texas summer it's been 123 deg in the shade. The sun reflected off the concrete flight line, a double whammy direct and reflected. Sheppard also in winter often was in the 10's and windy, nothing to stop the wind across the plains. Regs wouldn't allow us to remove our fatigue tops. We often connected an AC unit hose into the B-52 cockpit and get relief.
Believe the tabulation on the charts. I have sought and calculated the data and made my own charts. Discovered the data points when plotted form a tangential curve and do for each increment of degrees. If a temperature is in between interpolate. Hard to know any wind speed unless you have that instrument, which I had at one time. The curves vary at various points of temp & either humidity (heat index) or wind speeds (wind chill).
Parking airplanes on Alton Bay NH in February during our fly-ins on the ice, (FAA sanctioned runway) Google it for videos) I've been in 40 below temps all day with at least 40 mph winds, t'was chilly. Got use to it and didn't seek warmth. The flying club (Alton Bay Flying Club) has the fly-ins each February, conditions being right. Pilots come from MI, VA and in between to experience landing on ice, I've done it. Mentioned to inform, the cold isn't so bad. This informs about the cold side of temperatures.
I am looking for how many 100 or above days in a row we have had in the area this summer also how many we have had this year. We are located in the DFW area TX
Cowell, You can check the daily Weather History tool for temps last year; it's free. There's also a Customized Weather History tool for a small fee which makes it easier if you wish to pull multiple days and look at trends. http://www.almanac.com/weather/history