AUGUST 2021 MONTHLY SUMMARY ROCKVILLE 2.8 WNW MARYLAND
by Kevin Shaw, Observer
August 2021 had above average temperatures with
significantly above normal precipitation amounts
that were concentrated between the 9th and 28th.
As such there was only one monthly dry spell
starting on the 2nd and carrying through the 8th.
There were numerous wet spells at most other times,
most notably from the 9th-11th (1.63”) and from
the 25th-28th when daily thunderstorm action each
day totaled 1.07”.
My maximum temperature average (85.4°) was 1.1°
above normal but my minimum temperature average
(69.8°) was 5.4° above normal, resulting in the
mean temperature average of 77.6° turning out to
be 3.3° above normal. My total precipitation of
6.06" was 2.89” above the normal August value for
my station of 3.17”. There were 15 days with
measurable precipitation and 1 day with trace
amounts, most all between the 9th and 28th.
There were four relatively “cool” days in July
with max temperatures below 80° (74.4° on the
1st, 77.9° on the 2nd and 3rd, and 76.8° on the
7th – only the 1st was wet (0.32”) and the other
3 days were dry). There were only 4 days with
minimums below 65 and none below 60. There were
8 days with max temps of 90° or more, topped off
by the 94.4° max on the 12th. There was a
significant 5 day period between the 9th and the
13th with max temperatures of 90° or more.
The monthly maximum daily precipitation amount
of 1.02" was reached on the 10th with other
notable one day events of .81” on the 13th,
.97” a week later on the 20th and .70” a week
later on the 27th when we had our strongest
thunderstorm of the month when a greatest PWG
of the year was recorded (63 MPH from the W at
1509). Fortunately the power and other
accessories did not fail as a result of this
storm like what happened with the storm back
in July.
The extreme barometric pressure readings of
the month were rather muted but occurred 3
days of each other. The lowest value of 29.79”
on the 31st as Tropical Storm Ida was
approaching the area but rain held off till
early on September 1. The highest value of
30.24” occurred only a few days earlier on
the 28th at the end of our prolonged wet
spell during much of the month.
The highest dew point temperature reached
during the month was 80° recorded on the 13th
on a day with a significant thunderstorm
later in the day. There were 26 days with
dew point values of 70° or greater. The
lowest dew point value of 57° occurred on
the 2nd during our coolest period of the
month. There were only 4 days during the
month with dew points in the 50s, all
between the 2nd and the 5th.
August had 10 cloudy, 19 partly cloudy,
and 2 clear/sunny days, roughly about
normal for August. There were 392 cooling
degree days and 0 heating degree days
during the month. There were 5 foggy days
but only 4 windy days (30+ MPH but only 1
of 40+ MPH but it was a doozy as previously
detailed on the 27th ). Most days during the
month had PWG values in the moderate teens
(12) and twenties (15) range.
My maximum temperature frequencies included
8 days over 90°, 19 days at or over 80°, and
4 days between 70° and 79°. On the minimum
temperature frequency side of things, there
were 9 days between 60.0° and 69°, and 22
days of 70° or more. The coolest daily max
temperature day was 74.4° on the 1st while
the warmest daily min temp day of 74.2° was
reached on the 18th.
The diurnal range daily monthly average was
15.6° (- 4.3°). Our greatest daily range of
temperature was 23.7° on the 11th (93.9°-
70.2°). We had a total of 6 days with daily
ranges above 20°. Our lowest range of
temperature was 6.7° (74.4°- 67.7°) on the
1st , our coolest day of the month. There
were a total of 6 days with daily ranges
under 10° during August.
August 2021 was generally wet with only two
notable hot periods but still no real
extremes save for the very windy
thunderstorm on the 27th. Groundwater
reserves are currently in fairly good
shape from a wetter August and moderately
wet September so far. Extreme heat has
stayed away for the most part, keeping
lawns and gardens fairly green. The tropics
have flared up a bit on occasion, but have
been pretty quiet as far as our immediate
area goes. We shall see what, if any
activity will develop, including,
conversely, the coming of cooler fall
temperatures.
AUGUST 2021 – ROCKVILLE 2.8 WNW MARYLAND –
SUMMARY STATISTICS
Average high temperature 85.4° (+1.1°)
Average low temperature 69.8° (+5.4°)
Mean temperature 77.6° (+3.3°)
High temperature for the month (date) 94.4° (12)
Low temperature for the month (date) 60.0° (2)
Precipitation 6.06" (+2.89“)
Greatest daily amount (date) 1.02" (10)
Greatest storm total (dates) 1.63” (9-11)
2021 year-to-date precipitation total 25.08" (-2.51”)
Highest barometric pressure (date) 30.24” (28)
Lowest barometric pressure (date) 29.79” (31)
Peak wind gust (date/direction): 63 (27/W)
(USG data across the street)
Heating degree days for the month: 0
Cooling degree days for the month: 392
Greatest diurnal range (date): 23.7° (11)
Least diurnal range (date) 6.7° (1)
Number of days:
Fog 5
Windy 4
Thunder 7
Hail 0
Cloudy 10
Partly Cloudy 19
Sunny/Clear 2
Max temp = 90° 8
Min temp < 65° 4
Precip = 0.01” 15
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