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July 2019: Warmer and wetter than normal with abundant sunshine

July brought with it spells of hot, humid weather intermingled with more comfortable days. Rainfall was above normal but the number of days with rain was below normal.

Three heat waves were noted during July, two three-day spells and one four-day stretch. 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 these were the first of 2019. The high temperature tied a record on July 31 with 95, first set in 1916. A record high-low temperature was set on July 21 with 75, breaking 74 from 1977.

Temperatures at our state capital in Concord averaged 73.3 degrees and was a tie for the 10th warmest July since records began in 1869. Concord’s climate data is a little longer and more complete than Nashua’s data set.

July’s average temperature for the Gate City was 75.2 degrees, a surplus of 4.2 degrees. July was the 4th warmest out of 126 years with data since 1886.

The months’ high of 97 was recorded on the 22nd at the end of the month’s second heat wave. The low for the month was 54 degrees on the 8th.

High temperatures reached 90 degrees on 11 days during July, 6 more than normal but far from the record of 17 set in 1955. Humidity become much more noticeable during the second half of the month when dew point values shot up into the mid and even upper 70s a few times.

Dew point is the proper way to determine discomfort, not relative humidity. When dew point values rise to 65 degrees or higher most start to feel uncomfortable. When values exceed 70 everyone is uncomfortable. Values of 75 or more are outright miserable and are what residents of the Gulf Coast deal with all summer.

The highest reliably known dew point values in the southern New Hampshire of the past 40 years or so are 80 or 81. Values that high usually occur for a brief period and can occur after an afternoon shower which is followed by sunshine.

Dew point is the temperature at which the air would become saturated. If the dew point is 70 degrees there is the same amount of moisture contained in the air now matter if the air temperature is 80 or 100.

July was a wet month around the Nashua area during July but that was not the case throughout central New England. Nashua’s rain total of 6.66 inches was 2.78 inches above normal and ranked as the 9th wettest July out of 136 years.

While the month was wet the number of days with rainfall were below normal. Only seven days saw rainfall during July, four days less than normal.

That statistic tells us that when it rained, it rained heavily. Data in Hudson showed that it only rained during 7 percent of the hours during July, 5 percent less than normal.

Most of the rain occurrences during July were from thunderstorms or heavy showers. Some of these produced more than an inch of rain in less than an hour and created short-term flooding of streets and small streams.

To add to the confusion, not every location had the heavy downpours on the same days and some locations near Nashua saw little or no rain when a nearby town had a cloudburst.

Such is the normal nature of summer pop-corn showers and thunderstorms. One strong event noted in Hudson on July 31 produced 2.06 inches of rain in 45 minutes accompanied by 2 episodes of hail and a wind gust to 46 mph.

Just 4 miles to the west at the Pennichuck Water Works recording location only 0.27 inches fell and in Milford only 0.10 was recorded.

If you thought it was sunny during July, you were correct. Blue Hill Observatory in Milton, Massachusetts, saw 69 percent of the possible sunshine, a surplus of 12 percent. Blue Hill Observatory is the nearest location to Nashua that still records sunshine.

The National Weather Service stopped recording sunshine during the mid-1990s when switching from human observers to the mechanical observers known as ASOS. This “modernization” has since created questionable temperature and precipitation data along with the end of sunshine and snowfall measurements at most U.S. airports.

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.

To date, August has been lacking of any “dog day” weather, but the month is young. The Bermuda high tends to deflect the cold fronts that can bring a period of refreshing cool, dry air from southern Canada.

During the fall the Bermuda high gradually 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, far more than during the past few decades.

Doug Webster of Hudson is a senior meteorologist at Hometown Forecast Services in Nashua.

July Facts and Feats dating back to 1884

July 2019 Average Temperature

75.2 degrees, 4.2 degrees above normal

Warmest July

76.5, 1911

Coolest July

64.9, 1962

All-time July High

106, July 4, 1911

July 2019 High

97, July 22

All-time July Low

37, July 7, 1965

July 2019 Low

54, July 8

July 2019

Precipitation

6.66 inches, 2.78 inches above normal

Wettest July

9.21 inches, 1938

Driest July

0.45 inches, 1968

2019 Annual Precipitation to date

32.07 inches, 4.

28 inches above normal