The summer of the heat index 2010

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You know the old saying, “its not the heat but the humidity that gets ya”? Well this summer might be the best example you will find of that being the truth. While it has indeed been a hot summer from a air temperature standpoint we haven’t set many record daily or monthly records. One way to measure how hot the summer has been is the number of 90° days. This year we have hit that number 63 times when average is about 44. In 2007 we hit 90° or higher 76 times we are not likely to reach that and the all time record is 88 set in 1954. The top 5 most 90° days list is as follows.

 

88 1954

85 1925

76 2007,1993,1931

75 1956

73 1986

I’ll go out on a limb and say we won’t crack the top 5, but it’s still possible. The other way we measure the heat of the summer is the average temperature. This summer June was 3.8° above normal, July was 1.7° above and August so far has been 2.5° above. This is mainly due to the very warm nights. Which leads me to why this summer has felt so bad… HUMIDITY!!!!! Humidity makes the overnight low much higher than drier air.

Heat Index is the way we measure the affects of both the air temperature and humidity combined on the human body. If you don’t like math look away because here is how we calculate the heat index.

 

Heat Index = 16.923 + ((1.85212 x 10-1) x T)
                                  + (5.37941 x RH)
                                  – ((1.00254 x 10-1) x T x RH)
                                  + ((9.41695 x 10-3) x T2)
                                  + ((7.28898 x 10-3) x RH2)
                                  + ((3.45372 x 10-4) x T2 x RH)
                                  – ((8.14971 x 10-4) x T x RH2)
                                  + ((1.02102 x 10-5) x T2 x RH2)
                                  – ((3.8646 x 10-5) x T3)
                                  + ((2.91583 x 10-5) x RH3)
                                  + ((1.42721 x 10-6) x T3 x RH)
                                  + ((1.97483 x 10-7) x T x RH3)
                                  – ((2.18429 x 10-8) x T3 x RH2)
                                  + ((8.43296 x 10-10) x T2 x RH3)
                                  – ((4.81975 x 10-11) x T3 x RH3)

where T is the dry bulb temperature (°F) and RH is relative humidity (%)

 

This is much easier to understand

heat_index

 

So how has this summer compared to the past summers since 1972 for heat index? Here is a graph that shows total number of hours of heat index values of 100° or more at Charlotte Douglas airport.

graph3285

 

Here is the raw numbers of hours above certain Heat Index values.

Capture

 

We won’t know until the entire summer is over on September 21st how warm this summer actually was. The one thing I can tell you for sure, there has never been a more humid summer than this since 1972.