July 2018 saw above normal temps

July began with a developing heat wave that began on the final day of June. Hot and oppressively humid weather would linger across the region through July 6. Seven consecutive days would reach or exceed 90 degrees for a high temperature bringing the Gate City its fourth-longest heat wave on record.

The record remains nine days from Aug. 11-19, 2002, but the most intense period of heat remains from July 2-12, 1911, when nine out of 11 days saw readings over 90 and six days were over 100 degrees.

July 7 and 8, 1911, saw high readings of 87 that broke that spell into two heat waves. July 4, 1911, saw a high of 106, which is the all-time high for both Nashua and the state of New Hampshire.

The definition of a heat wave is three or more consecutive days with a high temperature of 90 degrees or higher.

We see an average of 1.6 heat waves per year in Nashua, and this was our first of the year. July 2 saw a record-tying high of 99, equaling the reading first recorded on this date in 1901. A record high-low temperature was established on July 24, with 72 beating out the 71 reading from 2011.

A look at our state capitals’ July temperatures show that the average temperature of 73.1 degrees was the 12th-warmest July since records began in 1869. Concord’s climate data is a little longer and more complete than Nashua’s data set.

While heat ruled during the first six days of July, the remainder of the month saw mostly normal July weather. Periods of slightly cooler than normal temperatures would mix in with typical July warmth. We did endure one more very humid spell later in the month as pure tropical air from the Bahamas made a home in New England.

Nashua’s average temperature for July of 74.8 degrees was 3.8 degrees above normal, ranking the month in a tie with 1887 as the fourth-warmest July since 1885. The warmest July remains 1911 with an average temperature of 76.5 degrees.

July was a very sunny month. At the Blue Hill Observatory in Milton, Massachusetts, 70 percent of the possible sun was recorded, a surplus of 13 percent. Blue Hill is the nearest location to Nashua with sunshine data. July was the sunniest July since 2001.

Rainfall was sparse during the first 17 days of July, a total of only 0.15 inches. Mother Nature turned on the water tap after that with 4.43 inches falling during the final two weeks of the month, giving Nashua a total of 4.58 inches.

Several episodes of thunderstorms would occur across southern New Hampshire during the later portion of July. Some of these storms would deposit torrential downpours and local flooding as well as a few lightning strikes.

Summer thunderstorms are well known to bring huge rainfall differences across very short distances. It is possible to have sunshine and no rain at one location with torrential rain and flooding just a mile or two away.

Most of the local rain gauges saw rain totals at above-normal levels, including 5.29 inches for Hudson and 5.76 inches at East Milford. The rain totals at all three locations did not come at the same time or on the same day due to the fickle nature of summer thunderstorms.

Nashua’s 2018 rain total stands at 25.30 inches of rain, 2.49 inches below normal. While we’re lagging a bit behind on rain for the year, we’ve had mostly timely rains, which have kept water levels near par and agricultural interests fairly happy.

Thunder was heard on six days in Hudson, one day more than normal. Thunderstorm frequency had been quite low through the middle of July but has picked up considerably during late July.

The “dog days of summer” are named for the occasional stretches of late summer weather with light winds, hazy skies and hot, humid weather. While hot, humid weather isn’t out of the ordinary, haze is observed much less than it was 40 years ago.

The Clean Air Act of 1970 did its job, leaving us with more blue skies during periods of hot, humid weather rather than the white skies and red solar disk as was commonly observed 40 years ago.

August has begun with some of the dog-day weather we often see at this time of year. The reason is the expansion of the Bermuda high during mid and late summer allowing southwest winds to import heat and humidity into our area from the southern U.S.

The Bermuda high tends to deflect the cold fronts that can bring a period of refreshing cool, dry air from southern Canada. As we move into September, the Bermuda high begins to lose out to the increasingly strong polar jet stream which starts to send cooler weather our way.

August sees the average daily temperature decline at an increasing pace as the month grows older. The day length also becomes noticeably shorter. Hurricanes can make an occasional visit to our area, but rarely produce major damage.

The last hurricane to make landfall in New England was Bob in 1991, so we are certainly overdue for a visit by such a storm. From the 1930s through the 1960s hurricanes visited New England every few years.

So far this summer, the tropics have been fairly quiet due to large amounts of dust moving westward across the tropical Atlantic from Africa.

July Facts and Feats dating back to 1884

July 2018 Average

Temperature

74.8 degrees, 3.8

degrees above

normal.

Warmest July

76.5, 1911.

Coolest July

64.9, 1962.

All-time July High

106, July 4, 1911.

July 2018 High

99, July 2, 4.

All-time July Low

37, July 7, 1965.

July 2018 Low

51, July 7, 8.

July 2018 Precipitation

4.58 inches, 0.70 inches above normal.

Wettest July

9.21 inches, 1938

Driest July

0.45 inches, 1968

2018 Annual

Precipitation to date

25.30 inches, 2.49 inches below normal.