Introducing the “Daytime Outdoor Pool Index”
A colleague of mine, Angela, insists that June is always starts cold in South Dakota. Clearly this June is extra cold, with daytime high temperatures averaging 6-7 degrees below normal in Sioux Falls, and the month is on pace to be the coldest-ever June in Rapid City.
My children concur with Angela’s hypothesis, based upon the lack of days spent at the neighborhood pool. So I decided to combine my kids’ observation and Angela’s hypothesis with the creation of a subjective barometer I will call the “Daytime Outdoor Pool Index”, or “DOPI” for short. It is not an unprecedented concept – farmers have an official index called growing degree days (GDD), and the energy people have indexes called heating degree days and cooling degree days (HDD and CDD), intended to reflect how much we operate our air conditioning and indoor furnaces.
In designing DOPI, I considered what parameters are essential for a good day at the pool. First and foremost, the public pools must be open. In the Northern Plains that generally means mid-May to mid-September. Secondly, it must be warm. Eighty degrees or better seems to be a nice round number, though the kids will agree to go to the pool if it as least 75 degrees early in the season. I will give half-credit for May days where the high temperature is between 75 and 79 degrees.
Sunshine is essential, since a healthy tan (a few shades short of a burn) seems to be desirable. I will decrease by one-quarter any pool day if the location receives less than half of its possible sunshine due to thick clouds. Another factor that will ruin an otherwise nice pool day is a strong wind. Even on a hot day, strong winds can make a body shivver when getting out of the water. So in DOPI, we will decrease by another one-quarter any pool day in which the average wind speed is over 15 miles per hour.
Putting together all of the numbers, here is how many acceptable pool days there have been in Sioux Falls, SD over the past few years:
So what does this prove? Absolutely nothing, except that this has been a lousy month to visit the local pool. And – perhaps – that there are too many meteorological indexes to keep track of.
