JULY 2019 MONTHLY SUMMARY ROCKVILLE 2.8 WNW MARYLAND
by Kevin Shaw, Observer

July 2019 was wetter and warmer than normal. My max temp (89.0°) was 2.7° above normal and my min temp (69.9°) was even a bit more significantly 4.2° above normal, resulting in the mean temperature (79.4°) to be 3.4° above normal. My total precipitation of 7.03″ was 3.20” above the normal July value for my station of 3.83″. There were
fewer but generally larger daily amounts of precipitation than in June leading to a bit drier than normal 9 days with measurable precipitation, Seven of those nine days fell during the first eleven days of the month when 5.75” was recorded (nearly 82% of the month’s total).

There were only 2 relatively cool days (max temps below 80°) during the month, both occurring on cloudy, rainy days on the 8th (2.86”) and 23rd (1.06”). In fact, those were the 2 wettest days of the month. From the 14th till the end of the month temps were frequently at or above 90° (11 such days when rounded). The warmest temperature for the month was 96.5° on the 21st, and the coolest was 62.2° on the 25th.

There were 9 days with measurable precipitation, highlighted by the monthly maximum of 2.86″ on the 8th during an unusually heavy morning thunderstorm. This was my 5th wettest day ever since records were started for this location back in January 2017. Three of the five wettest days I have ever recorded have occurred in July. Conversely there were 3 notably significant dry periods during July when no rain fell (12th-16th, 18th-22nd, 24th-31st). With the generally wet summer, these dry periods did not start showing any adverse trends in the vegetation in the immediate area.

The highest barometric pressure reading of the month of 30.30” occurred on the 27th, in the middle of our driest period of the month (8 days from the 24th-31st). The lowest reading was 29.74” on the 23rd on the day of our 2nd heaviest daily rainfall of the month.

The highest dew point temperature reached during the month was 80° on the 20th and 21st which unfortunately (for comfort’s sake), also occurred on the 2 hottest days of the month.  There were 26 days in July when dew point temps were 70° or higher, including 12 days above 75°, spread out throughout the month. The lowest dew point temperature value was reached on the 1st when a value of 56° was reached. There were only 4 days during the month when the dew point temps were in the 50s.

July had 7 cloudy days, 14 partly cloudy days, and 10 clear/sunny days with an unusual higher amount of sunny days due to the 3 long, dry spells during the month. There were 0 heating degree days and 447 cooling degree days during the month. There were 5 foggy days, 2 windy days, and 8 days with thunder.

Daily max/min temperatures didn’t vary as much as in the previous few months, a typical trend of the mid-summer period. My maximum temperature frequencies included 15 days over 90°, 14 days between 80° and 89°, and 2 days between 70° and 79°.  On the minimum temperature frequency side of things, there were 15 days between 60°
and 69° and 16 days above 70°. The coldest daily max temperature was 75.9° on the rainy 23rd while the warmest daily min temp of 76.4° was on the 21st, when the max temp during the month was also reached (96.5°).

The diurnal range daily monthly average was 19.1° (- 1.2°). Our greatest daily range of temperature was 30.1° on the 2nd (93.5°-63.4°). We had a total of 13 days with daily ranges above 20°. Our lowest range of temperature was 8.0° (76.2°-68.2°) on the 8th (our wettest day of the month). There were only 2 total days with diurnal temperature ranges of less than 10° throughout the month, occurring on the two wettest days of the month.

July 2019 was a typical mid-summer month, with heat, humidity and occasionally heavy thunderstorms predominating and conversely, some significantly long dry spells. Tropical storm Barry developed during mid July (11-19) in the Caribbean, and ravaged Louisiana with flooding rains but fizzled out before reaching our area. There weren’t any problems experienced with my weather station during the month thank goodness, save for my recurring VPs tipping bucket problems. . 

My daily data for July in PDF of my excel master spreadsheet: 

2019-07-Rockville-2.8-WNW

JULY 2019 – ROCKVILLE 2.8 WNW MARYLAND – SUMMARY STATISTICS

Average high temperature                          89.0°  (+ 2.7°)
Average low temperature                           69.9°  (+ 4.2°)
Mean temperature                                     79.4°  (+ 3.4°)

Precipitation                                               7.03″ (+ 3.20“)
Greatest daily amount (date)                     2.86″     (8)
Greatest storm total (dates)                     4.54”    (4-8)
2019 year-to-date precipitation total      30.03″ (+ 6.52”)

High temperature for the month (date)         96.5°   (21)
Low temperature for the month  (date)         62.2°   (25)

Highest barometric pressure (date)            30.30”  (27)
Lowest barometric pressure (date)             29.74” (23)

Peak wind gust (date/direction):                    N/A

Heating degree days for the month:                 0
Cooling degree days for the month:                447

Greatest diurnal range (date):                   30.1° (2)
Least diurnal range (date)                           8.0° (8)

Number of days:

Fog                            5
Windy                        2
Thunder                     8
Cloudy                        7
Partly Cloudy             14
Sunny/Clear              10
Max temp ≥ 90°         15
Min temp  <  60°         0
Min temp  =>  70°      16
Precip ≥  0.01”            9