I couldn’t let the day go by without commenting on the absolutely glorious weather we’ve been having. For today, we had a high of 81 degrees. With the dew point as low as 42 degrees, the humidity was a low 27% shortly after noon. These humidity levels are reminiscent of March (with equally March-like winds). The pleasant weather should continue through Friday, with higher humidity and a slight chance of showers over the weekend.

Overall, the May weather hasn’t been anywhere close to normal. We are on track to having one of the driest Mays ever, with only 8 tenths of an inch. Overall temperatures and humidities have been lower than normal as well.

One measure of the lower temperatures is the number of cooling degree days we’ve seen so far this year. Cooling degree days (and their complementary heating degree days) are a measure of how the temperature varies from 65 degrees. Temps above 65 bring more cooling degree days, while lower temperatures bring more heating degree days. So far this year, we’ve had just under 200 cooling degree days; last year at this time, we were at 300.

You can also look at the average relative humidity for this month, compared to more normal years. The mean relative humidity this month so far is 67%, compared to a 78% average from 2002-2004.

Our good weather is the result of a persistent major upper level low, or trough, over Eastern Canada, more typical of what we would see in winter rather than late spring. That low is wreaking havoc in the Northeast, where Boston had high temperatures this week in the upper 40s, and a major Nor’Easter is pounding the coast.

The low is preventing the normal pattern of warm, humid air moving from the Gulf Coast through Georgia, and north through the Mid-Atlantic States. Instead, we are getting drier, cooler air from the Northwest, which can’t follow its normal pattern across the Northeast because of the blocking low.

Forecasters predict that the Northeastern low is likely to break up sometime over the weekend, bringing us more typical weather for the start of June. On the other hand, the National Weather Service predicts lower than normal temperatures for our area through the first week of June. It all depends on how soon the trough on the East coast breaks up.