JUNE 2018 MONTHLY SUMMARY ROCKVILLE 2.8 WNW MARYLAND
By Kevin Shaw, Observer in Charge
June 2018 featured near normal rainfall and temperatures at my station, extrapolated from statistics compiled
at the three major airports in the DC area and published in the June NWS PRESTO report. There were a few
short hot spells with max temps of 90 or more (18th-19th and 29th-30th) but generally pleasantly cool temps
most of the days of the first half of the month (7 days with maximum temperatures less than 80° with 1 day
in the 60s) .Many of these cooler days (as is so common during the summer months) were cloudy, rainy days.
The highest temperature of the month was 93.7° on June 18, and the coolest was 54.2° just six days earlier
on the 12th. There were no really notable heavy precipitation days, just a lot of moderate amounts, topped by
the 0.93” on the 3rd, 0.82” on the 19th and 0.76” on the 2nd. A moderately wet period occurred from June
19 through the 24th during which 1.49” fell. There were 13 days with measurable precipitation, probably roughly
a normal amount for June.
As we approach the summer months, significant pressure differences become less important because among other
things they go away, unless we get some significant tropical activity with the usual low pressure associated with
tropical storms and/or hurricanes. June continued the trend started in May as the extreme highest pressure for
the month (30.25” on the 12th) and the extreme lowest (29.70” on the 5th) were once again rather muted. The
month had 11 cloudy days, 11 partly cloudy days, and 8 clear/sunny days.
There were 5 heating degree days and 248 cooling degree days during the month. There were only 4 foggy days,
only 2 days with thunder and 2 windy days (mostly during intense rain events). The windy day category is subjective
with no personal real data values to back it, just based on my descriptive email daily weather posts that are also
posted on weathertogether.net.
Daily max/min temperatures varied less during June compared with May. My maximum temperature frequencies
included 4 days of 90° or greater, 14 days between 80° and 89°, 11 days between 70° and 79°, and 1 day
between 60° and 69°. On the minimum temperature frequency side of things, there were 8 days between 50°
and 59°, 16 days between 60° and 69°, and 6 days at or above 70°. The coldest daily max temperature was
64.8° on the 11th and the warmest daily min temp was 73.4° on the 19th.
The diurnal range daily monthly average was 17.2°. Our greatest daily range of temperature was 25.9° on the 16th,
formed from a high of 85.9° and low of 60.0° as I was ramping up from a cooler period to one of our brief “heat
spells” of the month. We had a total of 9 days with daily ranges above 20°. Our lowest range of temperature was
7.1° (64.8°-57.7°) on the cloudy, wet 11th – our coolest day of the month. There were only 2 other days with
diurnal temperature ranges less than 10.0°, once again on cloudy, rainy days.
Recent changes to the station include a new base to the VP2 weather station, as the old one shifted too easily and
became slanted which can throw off the rainfall catch. Helping out is also a screen added to cover over the small
hole at the bottom of the gauge cone that will keep out pollen and leaf and twig litter, particularly pine needles from
the closeby pine tree. Unfortunately despite trimming some of the pine tree branches, the pine tree is still causing
excessive blowoff into the gauge, elevating the rainfall readings frequently compared to my official cocorahs rain
gauge. I am still constantly checking on my data quality frequently along with some of my Maryland weather cohorts.
I just added lightning detection equipment to my instrument arsenal.. I continue to occasionally (as time allows) submit
GLOBE Cloud observations, complete with submission of sky pictures at the time of the observation, usually timed with
the passage of satellites and/or solar noon (about 70 minutes past actual EDT noon). Please ask me any questions you
want at any time about my station setup and/or my data through any means available to you.
JUNE 2018 – ROCKVILLE 2.8 WNW MARYLAND – SUMMARY STATISTICS
Average high temperature 81.7°
Average low temperature 64.5°
Mean temperature 73.1°
Greatest daily amount (date) 0.93″ (3)
Greatest storm total (dates) 1.69” (2-3)
2018 year-to-date precipitation total 22.27″
High temperature for the month (date) 93.7° (18)
Low temperature for the month (date) 54.2° (12)
Highest barometric pressure (date) 30.25” (12)
Lowest barometric pressure (date) 29.70” (5)
Peak wind gust (date/direction): N/A
Heating degree days for the month: 5
Cooling degree days for the month: 248
Greatest diurnal range (date): 25.9° (16)
Least diurnal range (date): 7.1° (11)
Number of days:
Partly Cloudy 11
Max temp ≥ 90° 4
Min temp < 60° 8
Precip ≥ 0.01” 13