NATIONAL WEATHER SUMMARY

AUGUST 2018

1-4:  Widely scattered showers dotted the Plains, Midwest, and mid-South, accompanied by a turn toward cooler weather.  Weekly temperatures averaged at least 5°F below normal from the central Plains into the mid-South, as well as portions of the upper Great Lakes region.  Farther west, mostly dry weather prevailed from the Pacific Coast to the northern High Plains, while monsoon-related showers dotted the Southwest.  The Northwestern dryness, accompanied by temperatures that averaged more than 5°F above normal in some locations, favored small grain maturation and harvesting.  However, hot, dry conditions in northern California and the Northwest contributed to additional wildfire development and expansion.  Heat also persisted across the Far West and Desert Southwest.

 Early-week Northwestern heat led to daily-record highs in Hermiston, OR (107°F), and Ellensburg, WA (102°F).  In contrast, high temperatures failed to reach the 70-degree mark on July 29 in Illinois locations such as Lincoln (68°F) and Springfield (69°F).  Meanwhile in Texas, Brownsville reported triple-digit temperatures five times during the last 9 days of July, including a daily-record high of 100°F on the 31st.  Elsewhere in Deep South Texas, McAllen reached or exceeded 100°F on each of the last 16 days of July, as well as the first 4 days of August.  Farther west, Death Valley, CA, completed its hottest month on record, with a July average temperature of 108.1°F (previously, 107.4°F in July 2017).  Death Valley’s minimum temperature failed to fall below 100°F on 10 days during July, including each of the last 4 days of the month.  In southern California, it was the hottest July on record at several locations, including Palmdale (87.8°F; previously, 87.0°F in 1931) and Long Beach (77.9°F; previously, 77.5°F in 2006).  Western heat continued through week’s end, with Challis, ID, notching a daily-record high of 97°F on August 2, and San Diego, CA, logging consecutive daily-record highs of 85°F on August 23.  Conversely, August 2 featured daily-record lows in International Falls, MN (34°F); Fargo, ND (40°F); and Aberdeen, SD (40°F). The Mendocino Complex, an amalgam of the River and Ranch fires near Potter Valley, CA, became the largest wildfire in modern California history, with 75 residences destroyed and more than 290,000 acres of timber, brush, and grass scorched by August 6.  Farther north, the deadly and destructive Carr fire, near Redding, CA, destroyed nearly 1,100 homes and more than 500 other buildings, and charred 167,000 acres of vegetation. 

 

5-11: In drought-affected areas from Texas into the lower Missouri Valley, rain provided some relief to pastures and immature summer crops.  However, showers bypassed the northern Plains, where building heat—with late-week temperatures topping 100°F—favored small grain harvesting but rapidly depleted topsoil moisture. Hot, dry weather also dominated the West, promoting fieldwork but hampering wildfire containment efforts and further boosting irrigation demands.  Monsoon-related showers were mostly confined to the southern Rockies and the Desert Southwest.  Weekly temperatures averaged as much as 5 to 10°F above normal in the Northwest and more than 5°F above normal in several Northeastern locations.  In contrast, near- or slightly below normal temperatures stretched from the central and southern Plains into the lower Mississippi Valley.

 Winslow, AZ, posted five consecutive highs of 100°F or greater from August 5-9, tying or breaking a record high each day.  The highest reading during Winslow’s hot spell was 102°F on August 6 and 7.  Other daily-record highs in the Desert Southwest on August 6 included 116°F in Thermal, CA, and 114°F in Phoenix, AZ.  Record-setting heat also appeared on August 6 in the Northeast, where daily-record highs surged to 95°F in Burlington, VT, and Plattsburgh, NY.  Meanwhile, cool air briefly settled across the Northwest, resulting in daily-record lows in locations such as Pocatello, ID (43°F), and Worland, WY (44°F).  Later, however, Pocatello collected consecutive daily-record highs (102 and 100°F, respectively) on August 10-11.  Pocatello had last attained 102°F on July 6, 2007.  Meanwhile in Nevada, Reno set an annual record with 19 days of triple-digit heat— including 4 days in a row from August 8-11.  Reno’s previous record of 16 days had been set in 2017.  Late-week temperatures soared across the Northwest, where Stanley, ID, tied an all-time record with a high of 96°F on August 10.  Previously, Stanley had also attained 96°F on July 18, 1964.  Elsewhere in Idaho, Boise tallied a trio of daily-record highs (106, 110, and 104°F) from August 9-11, while Lewiston attained 111°F on the 9th.  In Montana, the week ended (from August 9-11) with three daily record highs in a row in locations such as Havre (101, 105, and 102°F) and Glasgow (101, 107, and 107°F).  In North Dakota, Williston (105 and 108°F) and Minot (103 and 106°F) reported consecutive daily-record highs on August 11-12.  With the latter reading, Williston also tied a monthly record originally set with a high of 108°F on August 7, 1949.

 

12-18: Hot, mostly dry weather dominated the northern Plains for much of the week, promoting small grain harvesting but depleting topsoil moisture in advance of the winter wheat planting season. However, late-week showers locally helped to reverse the northern Plains’ drying trend. Late-summer heat also covered much of the West, where weekly temperatures averaged at least 5°F above normal in many locations. In addition, dozens of wildfires remained active across northern California and the Northwest, resulting in degraded air quality due to widespread smoke. Western showers associated with the monsoon circulation were mostly limited to the Four Corners States and portions of the Great Basin. A few thundershowers reached the Northwest but contained little rainfall and resulted in some new, lightning sparked fires. Through August 20, U.S. wildfires had charred about 6.0 million acres of vegetation, well above the 10-year average of 4.9 million acres. California’s largest wildfire in modern state history, the Mendocino Complex near Clear Lake, grew to more than 400,000 acres, although containment approached 75 percent. Containment reached 90 percent on the Carr Fire, which has consumed nearly 230,000 acres of timber, brush, and grass near Redding, CA, and has destroyed 1,079 residences and more than 500 outbuildings. Meanwhile, early-week heat resulted in a monthly record-tying high of 108°F in Williston, ND, on August 12. Previously, Williston had attained 108°F on August 7, 1949. Elsewhere on August 12, triple-digit, daily-record highs included 106°F in Minot, ND; 104°F in Sheridan, WY; and 103°F in Turner, MT. With a maximum temperature of 105°F on the 12th, Greybull, WY, achieved its highest August reading since August 15, 2003, when it was also 105°F. Hot weather later shifted into the Great Lakes region, where daily-record highs for August 14 soared to 91°F in Sault Sainte Marie, MI, and 90°F in Rhinelander, WI. Toward week’s end, heat re-intensified across the northern High Plains and the Northwest. Following consecutive highs of 107°F on August 10-11, Glasgow, MT, posted a high of 102°F on August 17. Late-week heat also affected southern Texas, where McAllen logged a daily-record high of 105°F on August 17.

 

19-25: In contrast, hot, dry weather returned to the south-central U.S., boosting temperatures to 100°F or higher in many locations.  Dry weather on the southern Plains followed drought-easing rainfall, but short-term dryness intensified in the western Gulf Coast region.  Meanwhile on the northern Plains, small grain harvesting proceeded with only minor delays, despite below-normal temperatures.  In fact, weekly temperatures averaged at least 5°F below normal across large sections of the northern and central Plains.  Farther west, however, late-season heat persisted in the Desert Southwest, where temperatures locally averaged more than 5°F above normal.  Showers associated with the monsoon circulation were heaviest in the Four Corners States, while little or no precipitation fell in California, the Great Basin, and the Northwest.  Smoke associated with dozens of Northwestern wildfires resulted in ongoing air-quality degradation. 

 

26-31: Hot, humid weather covered much of the South and East, maintaining a rapid pace of summer crop development.  Hot, dry weather gripped the southern Plains, where weekly temperatures averaged at least 5°F above normal.  In contrast, readings averaged more than 5°F below normal in numerous locations across northern sections of the Rockies and High Plains.  Elsewhere, isolated Western showers were limited to the Four Corners States and the nation’s northern tier.  Wildfire containment efforts in the Northwest were aided by the rain (and high elevation snow), as well as cooler conditions that extended southward into California. An impressive heat wave in the southcentral U.S. continued through week’s end.  High temperatures in McAllen, TX, reached or exceeded 100°F each day from August 6-31, followed by a daily-record high of 106°F on September 1.  Triple-digit, daily-record highs were established in many other Texas locations, including El Paso (102°F on August 29); Dalhart (101°F on August 30); and Lubbock (100°F on August 27).  Meanwhile, a surge of late-season heat also engulfed the lower Great Lakes region and the Northeast.  Providence, RI, posted consecutive daily-record highs of 95°F on August 28-29.  Other record-setting highs for August 29 included 98°F in Boston, MA, and 97°F in Burlington, VT.  With a monthly average temperature of 68.9°F (5.3°F above normal), Caribou, ME, completed its warmest August on record (previously, 68.2°F in 2015).  In contrast, chilly air settled across the Northwest.  Pocatello, ID, posted consecutive daily-record lows (34°F both days) on August 28-29.  Elsewhere on the 29th, daily-record lows in Wyoming dipped to 37°F in Casper and 38°F in Worland.  At month’s end, even colder air settled across the northern Rockies, where West Yellowstone, MT, notched a daily record-tying low of 18°F on August 31.

Jim G. Munley, jr.
http://www.jimmunleywx.com