August 2018 saw milestone warmth; was wet, very humid

If you like summer heat and humidity, then August was your month. Nearly non-stop tropical humidity would keep air conditioners buzzing through the month. A persistent upper level ridge through the eastern U.S. allowed the Bermuda High to flex its’ muscles this summer.

While cooler-than-normal readings covered much of the central and southern U.S. during August, the Northeast would see tropical air make a home. The excessive amounts of humidity helped fuel heavy rains and flooding across the Mid-Atlantic and Northeast, where some parts of northern Pennsylvania saw more than 20 inches for August alone.

For those of us across southern New Hampshire, very warm, very humid weather typical of places like South Carolina or Florida was only broken up by a few days of more seasonable weather during the third week of August.

Nashua set a new record for warmth during August with an average temperature of 74.3 degrees, surpassing 73.2 degrees from 2012. August was 5.0 degrees above normal. The average low was 64.3 degrees, also a record for the month bettering 61.8 degrees from 1988.

Most of the warmth of August was accountable to the excessive humidity. As we all know, air with lots of moisture retains heat and that’s what happened last month. The average low for Nashua was 6.7 degrees above normal, while the average high was 3.2 degrees above normal.

One daily high temperature record was tied on the 30th, when the mercury reached 95 degrees, tying the mark last set in 1973. Record high-low temperatures were recorded on the 9th with 71, and the 30th with 72 breaking the readings of 70 and 69 from 1984, respectively.

Meteorologists measure the amount of moisture in the air using dew point. In Hudson, I recorded an average dew point during August of 67 degrees, 3 degrees higher than any other August reading in 33 years. The all-time record is 68 degrees from July 2013.

Average monthly dew point values around here are typical 60 or 61 during the summer. During this summer, there were numerous days with readings reaching torrid levels in the mid- and upper-70s. These are values common to Florida and the Gulf Coast.

The reason dew point is used to determine how humid it feels is that when the dew point is, for example 68, there is always the same amount of moisture in the air no matter what the temperature is. You’ll feel uncomfortable with a 68 dew point whether the temperature is 70 degrees or 90 degrees, worse at 90 even though the relative humidity is much lower. Dew points over 70 are oppressive feeling.

Temperatures toped 90 degrees on eight days, five more than normal. We also saw one heat wave from Aug. 6 through the 9th, our second of the summer. A heat wave is defined as three or more consecutive days with temperatures reaching 90 or higher.

The warm nights of August also produced a record-tying event. The monthly low of 53 degrees tied the same value from 1901 for the warmest monthly low recorded during August.

Cooling degree days totaled 296 during August, a new record topping the 266 recorded in 1988. This number is 138 (87 percent) above normal, and is why your electricity bill will be higher than normal if you used air conditioning.

Rainfall was heavy during August, but all of it fell during the first three weeks. The total of 7.08 inches for Nashua was 3.17 inches above normal and ranked as the 11th wettest August of record during the past 135 years of record.

Rainfall totals were quite variable around the region due to the typical hit and miss nature of torrential summer downpours. One location may see a torrent of rain topping an inch while a mile away no rain falls at all.

A record daily rainfall total was recorded on the 12th, when 1.90 inches surpassed the 1.76 amount from 1971. The 2018 rain total now stands at 32.38 inches, just 0.68 inches above normal.

In our state capital of Concord, a new August monthly rainfall record was set with 10.67 inches.

Official summer (June-August) brought record warmth and wetter than normal weather to the Gate City.

Nashua’s average temperature of 71.9 degrees broke the previous warm record of 71.5 degrees from 2016. June was just slightly warmer than normal, but both July, fourth warmest on record, and August, warmest of record, brought us a new summer warm standard.

The summer rainfall tally of 15.10 inches was 3.71 inches above normal, tying for 13th place from wettest to driest out of 135 years. The first half of summer from June 1 through mid-July was quite dry, while the second half of summer was very wet.

Twenty-one days reached 90 or more during the summer, 10 days more than normal, but far from the record of 33 days set in 1955.

Meteorological fall began Sept. 1, and average temperatures fall about 10 degrees this month. September is the peak month for tropical storms to visit New England, but cooler Canadian air also starts to have more of an impact as the month moves along.

This year marks the 80th anniversary of the Great Hurricane of 1938, by far the most destructive storm to strike New England during the past two centuries. New England has not seen a hurricane landfall for 27 years, with Hurricane Bob of 1991 being the last to affect us.

September can bring us some of the finest weather of the year, with this being the sunniest month by average. Very comfortable temperatures, dry air and infrequent rainfall can make for pleasant outdoor conditions. As we’ve seen to start this September, though, heat and humidity can still make it feel like mid-summer at times.

Weather & Climate is written by Doug Webster a Hudson resident and senior meteorologist at DTN/The Progressive Farmer, a division of Schneider Electric in Andover, Mass.