April and the Nineties
Posted April 27, 2009
Dave Barry might suggest that title could make a good band name, but of course I'm referring to the stretch of hot weather we find ourselves in as we close out this fourth month of the year. So far at the Raleigh-Durham airport, we've hit 90 or above two days in a row and have at least a reasonable chance of reaching 90 today, though it certainly wouldn't be impossible for us to come up a degree or two shy as well. Quite a few people have asked how out of character these temperatures are for this time of year.
The answer falls in the realm of "quite unusual, but by no means unheard of" as shown by the fact that our normal high temperature (more or less the 30-year average from 1971-2000) over the past couple of days is in the mid 70s, with a standard deviation of about +/-8.4 degrees, meaning that most of the time our highs this stretch of dates fall between about 67 and 82. On the other hand, our record highs for the weekend, today and Tuesday are 92 (which we tied on Saturday), 93, 92 and 90 respectively, meaning that we can expect to be this hot this time of year at least on rare occasion.
Following our 92 on Saturday, William Schmitz of the Southeast Regional Climate Center sent around a nice summary of all the 90+ days that have ever been observed at RDU in the first four months of the year. It showed that we have been as warm as 92 in March, though only once and that was in 1945. We've made it to 90 or higher 37 times in April since then, with the hottest April reading a lone 95 on the 23rd in 1980.
If we make it to 90 today, that will be three days in a row at 90 or higher, something we've accomplished in April three times before, in 1985, 1990 and 2002. In 1960, we topped that with 90 or above four straight days from the 23rd through the 26th. While equaling that mark wouldn't be impossible this year, the odds appear slim as we have at least a chance at coming up short today, and it also appears some air that originated over the ocean waters east of SC and GA and that is intrinsically a bit cooler, will make its way around a high pressure ridge and up into our area to give us an even better shot of holding in the upper 80s tomorrow.
If there's some good news in all of this, it's that this time of year we usually don't see the humidity spike along with the really hot temperatures, so our dew points have mainly stayed in the 50s and there isn't much if anything in the way of a "heat index factor." This means a temperature of 91 pretty much "feels like" 91 as opposed to the upper 90s that might apply on a humid summer day. Even so, take it a little easy outdoors if you can the next day or two, and then we should see temperatures moderate some later this week.