May brought warm temperatures and drier weather

Last month I wrote a look back at weather for the month of April that focused on how gray and wet it turned out for many of us. May brought a bit of a turnaround, as we ended the month with an average temperature that was several degrees above normal. Rain for many of us ran anywhere from a little to considerably below normal with a few exceptions south and east of about Wilson.

The first graph here shows that our May average temperature at RDU came in about 3.6 degrees above normal. For my electric bill, at least, that worked out to a pleasant value of 71.1 degrees, well above the coolest May on record from 1992, but still trailing the hottest (1896) by a decent margin.

Compared to the rainy April, we ended up with a notably less wet month of May, with the second graph showing that the RDU rain gage totaled up to less than a third of an inch below normal. This was plenty of rain compared to the dry conditions shown from 1926, but on the other hand May of 1901 saw over triple that amount for Raleigh.

For quite a few of us, though, the number from RDU was a little misleading, as shown in the map that contours the percentage of normal precipitation estimated by a combination of radar and gage sites for central NC. This map, from the National Weather Service Precipitation Analysis site, covers the 30 days ending with May 31.

It shows that while a small pocket near the airport came close to normal, many of us saw rainfall amounts that only amounted to about 30 to 70 percent of normal, and parts of southwestern Wake, Chatham and Orange counties, along with many areas farther west, came in with estimates of under 25 percent (red shading). The map shows more abundant rain toward the central and southern coastal plain, some of which traces back to the passage of Tropical Storm Ana early in the month.

A couple of other statistics of note for the month include the fact that we had measurable rain on eight days, compared to a normal of 10, and had over an inch of rain on one day (the 19th, when the airport recorded 1.38"). Historically, we have an inch or more of rain in a single day in May about five years out of 10.

We reached 90 degrees or higher on two days during the month, which matches the normal for that statistic.

The highest wind recorded at RDU was a peak of 35 mph, and for those of you who follow this, we recorded 20 heating-degree days for the month (34 fewer than normal) and 214 cooling-degree days (66 more than normal), both consistent with a month with average temperatures warmer than normal.

We're heading into "meteorological summer" this week with a very warm start, but it appears a front stalling over the area, combined with a slow moving, weak upper level low, will keep us a little cooler for a few days through midweek, thanks to more cloud cover and a better chance of showers and storms than we've experienced over the past several days.