By Kevin Shaw, Observer in Charge

May 2018 featured significantly above normal rainfall and temperatures in the region, based on statistics compiled
at the three major airports in the DC area and in general corroboration with my own statistics. There were generally
warm temperatures all month except for 5 days in the 60s during some of our 16 rainy days during the month.
Most of the warm days were in the 80s, save for 2 days near the beginning of the month that just tipped over the
90° mark. Extremes in temperature were quite muted this month. The highest temperature of the month was 90.5°
on May 3, and the coolest was 46.4° just two days earlier on the 1st. There were no really notable heavy
precipitation days, just a lot of moderate amounts, topped by the 4 days of just over an inch during the month
(The 1.13” total on the 15th was the greatest daily amount for the month). A particularly wet period (May 13-19)
occurred with 7 straight days of measurable precipitation totaling 4.77” and was about 67% of the total monthly amount
(6.68”) for May 2018. There were 16 days with measurable precipitation, assuredly well above the normal amount.

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. May started to show this pattern as the extreme highest pressure for the month (30.25” on the 8th)
and the extreme lowest (29.80” on the 10th) weren’t nearly as large apart as in the colder months. But please note that
the extreme values still exhibit the seemingly usual pattern of not being very far apart in days. The month had 13 cloudy
days, 10 partly cloudy days, and 8 clear/sunny days.

There were only 16 heating degree days and 174 cooling degree days during the month. There were 11 foggy days, 7
days with thunder and 6 windy days (mostly from thunderstorms). 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

Daily max/min temperatures varied less than April throughout May. My maximum temperature frequencies included 2
days of 90° or greater, 16 days between 80° and 89°, 8 days between 70° and 79°, and 5 days between 60° and
69°. On the minimum temperature frequency side of things, there was 1 day between 40° and 49°, 11 days between
50° and 59°, 17 days between 60° and 69°, and 2 days at or above 70°. The coldest daily max temperature was
66.7° on the 18th and the warmest daily min temp was 71.9° on the 26th.

The diurnal range daily monthly average was 18.6°. Our greatest daily range of temperature was 35.8° on the 2nd°,
formed from a high of 87.8° and low of 52.0° as I was in short transition between the coldest and warmest
temperatures of the month on the 1st and 3rd. We had one more day with a range over 30° (33.2° on the 1st)
and an additional 10 days with daily ranges above 20°. Our lowest range of temperature was 3.6° (67.7°-64.1°)
on the 17th. It was one of our cloudy, rainy days of the month. There were 4 other days with diurnal temperature
ranges less than 10.0°, mostly on cloudy, rainy days.

With yet another month to study the most recent instrument changes made in mid-August, data appears to be stable
and an overall data quality improvement success. I am still constantly checking on my data quality frequently along with
some of my Maryland weather cohorts. I am about to add a lightning detection component to my system. I had problems
with pollen clogging my tipping bucket gauge during May, which inhibited my capacity for adding precipitation timing and
max rain rates to my daily records. I also have continued as close to daily (as time allows) GLOBE Cloud observations,
complete with submission of sky pictures at the time of the observation, usually timed with the passage of satellites and
also 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.


Average high temperature 79.4°
Average low temperature 60.8°
Mean temperature 70.1°

Precipitation 6.68″
Greatest daily amount (date) 1.13″ (15)
Greatest storm total (dates) 4.77” (13-19)
2018 year-to-date precipitation total 18.50″

High temperature for the month (date) 90.5° (3)
Low temperature for the month (date) 46.4° (1)

Highest barometric pressure (date) 30.25” (8)
Lowest barometric pressure (date) 29.80” (10)

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

Heating degree days for the month: 16
Cooling degree days for the month: 174

Greatest diurnal range (date): 35.8° (2)
Least diurnal range (date): 3.6° (17)

Number of days:

Fog 11
Windy 6
Thunder 7
Cloudy 13
Partly Cloudy 10
Sunny/Clear 8
Max temp ≥ 90° 2
Min temp ≤ 32° 0
Precip ≥ 0.01” 16


About dabourphoto

Professional Photographer
This entry was posted in Uncategorized. Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s