NATIONAL WEATHER SUMMARY
MAY 2021
2-8:
Mostly dry weather prevailed west of the Rockies, aside from a few showers in
the Pacific Northwest. Combined with warmth, dry, sunny weather from California
into the Southwest has prematurely eliminated most of the 2020-21 snowpack.
Meanwhile, portions of the northern Plains received muchneeded precipitation
(rain and wet snow). Weekly totals topped an inch at several locations in
Montana, southwestern North Dakota, and northern South Dakota. However, mostly
dry weather persisted across the northeastern one-half of North Dakota,
extending eastward to Lake Superior. Elsewhere, generally nearor below-normal
temperatures east of the Rockies contrasted with very warm weather from
California into the Rio Grande Valley. Southern Florida was an exception,
remaining warm. Weekly temperatures averaged more than 5°F below normal in
scattered locations from the northern Plains into the Ohio Valley, but were at
least 5°F above normal across portions of peninsular Florida and from California
into the Southwest. Early-week temperatures topped 90°F across the southern High
Plains, with Borger, TX, posting a daily-record high of 96°F on May 2. Scattered
daily-record highs were also reported in other areas, including California,
Florida, and southern Texas. Daily-record highs included 107°F (on May 3) in
Laredo, TX, and 96°F (on May 5) in Lakeland, FL. During the second half of the
week, warmth began to expand eastward across the West. Daily-record highs
reached 92°F (on May 6) in Lewiston, ID, and 88°F (on May 7) in Greybull, WY. In
contrast, unusually cool air settled across the northern Plains and upper
Midwest, resulting in multiple freezes that continued to slow winter wheat
development and limit emergence of spring-sown crops. In the Northwest,
late-week freezes were reported at some interior locations. At times, scattered
frost extended as far south as the central Plains and the Corn Belt.
Daily-record lows were set in several locations, including Jamestown, ND (22°F
on May 4), and Eau Claire, WI(27°F on May 8). Elsewhere on May 8, daily
record-tying lows of 32°F were noted in Cedar Rapids, IA, and Moline, IL. From
May 3-11, Grand Forks, ND, reported nine consecutive hard freezes, with low
temperatures of 28°F or below. The only other instance of at least nine
consecutive hard freezes in Grand Forks during May was May 1-9, 1954. In
addition, Grand Forks has reported at least nine hard freezes during all of May
in only five other years: 1907, with thirteen hard freezes; 2002, with eleven;
1929, with ten; 1945, with nine; and 1954, with nine.
9-15:
Little or no precipitation fell across the nation’s northern tier, especially in
the Northwest and from the Dakotas to Michigan. Drought affected sections of the
North continued to experience stress on rangelands.
West
of the Rockies, very warm, mostly dry weather exacerbated the effects of
expansive drought; impacts included unusually heavy irrigation demands;
significant stress on rangeland, pastures, and rain-fed crops; premature melting
of mountain snowpack; and an enhanced wildfire threat. Weekly temperatures
averaging more than 5°F above normal were common across California, away from
the Pacific Coast. In contrast, another spring cool spell resulted in
significantly below-normal temperatures in most areas east of the Rockies.
Weekly temperatures averaged at least 5°F below normal across much of the
Plains, Midwest, mid-South, and mid-Atlantic. Readings averaged as much as 15°F
below normal in scattered locations across the middle Mississippi Valley. In
addition, temperatures remained below 80°F throughout the week across the
northern half of the U.S., excluding the interior Northwest. Freezes across the
North continued to slow the development of winter grains and the emergence and
growth of spring-sown crops, including corn, soybeans, and spring wheat.
Scattered frost occurred as far south as the central Plains and the southern
Corn Belt.
Hot
weather led to daily-record highs for May 9 in Del Rio, TX (106°F), and Naples,
FL (93°F). Meanwhile, warmth briefly affected areas along the Pacific Coast. In
California, record-setting highs for May 10 reached 94°F in Napa and 84°F at the
San Francisco Airport. In contrast, unusually cool air settled across the Plains
and Midwest. On May 11, daily-record lows dipped to 21°F in International Falls,
MN; 25°F in Eau Claire, WI; and 30°F in Muskegon, MI. On the central and
southern Plains, where cloudy, damp weather prevailed, high temperatures on May
11 remained below the 50-degree mark in Goodland, KS (46°F), and Amarillo, TX
(49°F). Later, Raleigh-Durham, NC, reported a May 12 high of 57°F—more than 20°F
below normal. During the second half of the week, numerous daily-record lows
were reported across the East and Midwest. Danville, VA, notched a daily-record
low of 37°F on May 13. Consecutive daily-record lows occurred on May 14-15 in
Raleigh-Durham (37 and 40°F, respectively) and Jackson, TN (40 and 42°F).
Late-week, daily-record lows dipped below the 40-degree mark in Cape Girardeau,
MO (39°F on May 14), and Parkersburg, WV (36°F on May 15).
16-22:
Short-term dryness in the East
reduced topsoil moisture for pastures and recently planted summer crops. Weekly
temperatures averaged at least 5°F below normal in portions of several areas,
including central and western Montana, the Far West, and the southcentral U.S.
In contrast, warmth prevailed from the upper Midwest into New England. Readings
averaged more than 10°F above normal in several places from Minnesota to Maine.
As the week began, cool air remained in place across the Southeast. In Florida,
record-setting lows for May 16 dipped to 50°F in Jacksonville and 59°F in
Leesburg. Several days later, a warming trend commenced across the Midwest and
Northeast, while chilly air settled across the northern High Plains and the
Northwest. By May 19, daily-record lows included 26°F in Kalispell, MT, and 33°F
in Quillayute, WA. From May 20-22, Great Falls, MT, reported three consecutive
daily-record lows of 26°F. A trio of daily-record lows also occurred from May
20-22 in Montana locations such as Billings(32, 31, and 31°F); Helena (28, 27,
and 29°F); and Holter Dam (29, 25, and 25°F). In addition, May 20-21 snowfall in
Montana totaled 7.8 inches in Helena and 5.1 inches in Great Falls. Other
Montana snowfall totals during that 2-day period included 6.8 inches in Havre
and 4.0 inches in Lewistown. West Yellowstone, MT, reported 10 inches of snow in
a 24-hour period on May 21-22. Maximum temperatures remained below the freezing
mark on May 21 for the first time on record in Montana locations such as
Lewistown (high of 29°F), Great Falls (30°F), Cut Bank (30°F), and Ennis (31°F).
Late in the week, record-setting temperatures expanded far beyond Montana.
Daily-record lows included 25°F (on May 21) in South Lake Tahoe, CA; 25°F (on
May 22) in Marysvale, UT; and 38°F (on May 22) in Kingman, AZ.
Strong winds accompanied the Southwestern cool spell; Arizona gusts on
May 22 were clocked to 61 mph in Springerville, 59 mph in Winslow, and 55 mph in
Flagstaff. Meanwhile in the Northeast, the second half of the week featured an
impressive, early-season warm spell. Record-setting highs for May 20 reached
92°F in Burlington, VT, and 90°F in Buffalo, NY. Two days later, daily-record
Eastern highs for May 22 soared to 94°F at Atlantic City, NJ, and New York’s JFK
Airport.
23-29:
Lower Southeastern dryness, accompanied by an early-season hot spell,
resulted in further reductions in topsoil moisture.
Seasonably dry weather prevailed in California and the Southwest, where
late-week heat complicated an already serious drought situation by severely
stressing dryland crops and boosting irrigation demands.
Although much of the country experienced near- or below-normal temperatures,
several days of hot weather affected the middle and southern Atlantic States. In
addition, heat began to build late in the week across the Far West. Weekly
temperatures averaged at least 5°F above normal at numerous mid-Atlantic
locations. In contrast, cooler-than-normal conditions—with temperatures
averaging more than 5°F below normal in many places—covered large sections of
the northern Plains, upper Midwest, and interior Northwest. Lateseason freezes
were reported in several areas across the nation’s northern tier, especially
from North Dakota to Maine, burning back tender vegetation such as emerged
summer crops. Scattered, late-week frost was noted in a broader area across the
northern Plains, upper Midwest, Great Lakes, and interior Northeast. As the week
began, record-setting warmth continued in the East. Record-setting highs for May
23 included 94°F in Wilmington, DE, and Atlantic City, NJ. Southeastern heat
lingered for several additional days. Daily-record highs soared to 98°F (on May
24) in Lumberton, NC; 95°F (on May 26) in Richmond, VA; and 98°F (on May 27) in
Wilmington, NC. There was also a brief, mid-week heat surge into the Great Lakes
and Northeastern States. In Michigan, daily-record highs for May 25 rose to 90°F
in Lansing and Battle Creek. In Maine, record-setting highs for May 26 climbed
to 91°F in Millinocket and 89°F in Houlton. Farther west, however, the week
began on a chilly note. Western daily-record lows for May 23 dipped to 20°F at
Utah’s Bryce Canyon Airport and 22°F in Flagstaff, AZ. Temperatures quickly
rebounded, though, as Ramona, CA, experienced a daily-record low (34°F) on May
23, followed the next day by a daily-record high (91°F). Late in the week, a
significant, late-season push of chilly air settled across the northern Plains,
Midwest, and Northeast. On May 28-29, Minnesota locations such as Hibbing (21
and 22°F, respectively) and Duluth (30 and 29°F) closed the week with
consecutive daily-record lows. From May 28-30, Massena, NY, reported three
consecutive freezes (32, 29, and 32°F)—the first freezes since late April in
that location. Freezes and daily-record lows occurred on May 29 in locations
such as Rhinelander, WI (26°F); Livingston, MT (29°F); and Eau Claire, WI
(32°F). Eau Claire’s only later final spring freezes occurred on June 12, 1903,
and June 6, 1897; readings of 32°F were also reported on May 29, 1965 and 1966.
Meanwhile in northern Iowa, Hampton’s low of 32°F on May 29 represented its
second-latest spring freeze on record, trailing only May 31, 1897—and tied with
May 29, 1947. In Binghamton, NY, the temperature remained below the 50-degree
mark on 3 consecutive days from May 28-30, peaking at 49, 45, and 48°F.
Jim G. Munley, jr.
http://www.jimmunleywx.com
