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Wildfires National Interagency Coordination Center (208) 387-5512
Agriculture USDA World Agricultural Outlook Board (202) 720-3508
USDA National Agricultural Statistics Service (202) 720-2157
Joint Agricultural Weather Facility (202) 720-7917
Drought Planning National Drought Mitigation Center (402) 472-6707
*There are 13 National Weather Service River Forecast Offices throughout the
U.S. that provide water supply forecasts. Call the above number for the River
Forecast Center with responsibility for your area of interest.
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SPECIAL CLIMATE SUMMARY 96/4
SUMMER 1996 CONDITIONS IN NORTH AMERICA
Issued September 25, 1996
Most of the central and eastern United States experienced a wet and cool Summer (June - August) while
excessive heat, minimal precipitation, and expansive wildfires affected much of the West. Heavy rains over the
central and south-central Plains, the southern Rockies, and parts of Arizona provided relief from the severe
drought that impacted these regions during the previous 8 months. However, over most of the North American
mid-latitudes, the basic temperature and precipitation patterns which developed in October 1995 (warm and dry
in the West; cool and wet in the East) generally persisted through Winter, Spring, and Summer 1996 with only
a few significant breaks (most notably late May and late August). This corresponded to the persistence of
upper-level ridging (northward jet-stream displacement) over the West, and upper-level troughing (southward
jet-stream displacement) through the Great Lakes and the Northeast.
Frequent cloudiness and precipitation often kept highs below 90F across areas to the north and east of the
central Great Plains, in dramatic contrast to the excessive heat that periodically covered these regions last
Summer (Figure 1). The lack of hot days has been noteworthy over the southern Appalachians, the lower Northeast,
and the mid-Atlantic. From northeastern Kentucky northeastward through West Virginia, Pennsylvania, and
southern New York, many locations (except in the higher elevations) reported highs at or above 90F on 20 - 33
days during Summer 1995. In contrast, highs in these areas reached at least 90F on 5 or fewer days this Summer,
with 6 to 10 days of 90F+ heat reported in the eastern Ohio Valley. From Philadelphia, PA southward to
Richmond, VA, the mercury climbed to at least 90F on 40 to 44 days during Summer 1995, including all-time
records for consecutive days with 90F+ heat at Philadelphia, PA (21), Baltimore, MD (25), and Richmond, VA
(27). This year, however, highs reached at least 90F on only 3 days near Philadelphia, and 10 to 15 days farther
south as Washington, DC approached its all-time record for consecutive summer days WITHOUT reaching 90F
(35 from July 18 - August 21; the all-time summer record is 41). Farther west, Midway Airport in Chicago, IL
reported 13 days of 90F+ heat and an extreme maximum of 94F (on 6/27 and 6/29) this Summer, compared to
32 days with 90F+ maxima and an all-time record high of 106F (on 7/13) during June - August 1995.
Despite the unseasonably low number of hot days across the northeastern quarter of the country, Summer
1996 average temperatures were only slightly below normal across most of the central and eastern United States
(Figure 2). June temperatures actually averaged above normal across the mid-Atlantic, Northeast, and Great
Lakes region, but from July 1 through August 19, departures of -2F to -5F covered a large portion of the central
and eastern states. Again, the persistence of sub-normal temperatures was more impressive than the magnitude
of the negative anomalies. Some locations reported more than 25 successive days with subnormal daily-average
temperatures.
Locally inundating rains fell on parts of the southern and western Great Lakes region, the central
Appalachians, the mid-Atlantic, and the Northeast, resulting in the 2nd wettest June-July period in 102 years
of record for the Northeast Region as a whole (1972 was the wettest), according to the Climate Prediction Center
and the National Climatic Data Center (Figure 3). Despite subnormal August rains in many areas, Summer 1996
featured 15 to 30 inches of rain at numerous locations east of the Mississippi River and north of the Gulf Coast
states, particularly northern sections of Illinois and Indiana, the central Appalachians and Piedmont, eastern
North Carolina, the East Coast Megalopolis from Washington, DC northeastward to New York, NY, and
northwestern New England. Most locations east of the Mississippi River (except parts of the south Atlantic
region) recorded above-normal rainfall, with at least 150% of normal soaking parts of the mid-Atlantic,
east-central Appalachians, Great Lakes region, and lower Mississippi Valley (Figure 4). Some of the rain east of
the Appalachians fell in association with Tropical Storm Arthur, which skirted the North Carolina coast in late
June, and Hurricane Bertha, which traversed eastern North Carolina, the mid-Atlantic, and the Northeast in
mid-July. Much drier weather covered the northeastern quarter of the country in August, with parts of New
England experiencing record or near-record low precipitation totals, but the large June-July amounts measured
across the region pushed Summer 1996 areally-averaged rainfall totals well above the 102-year median value.
Excessively high daily rainfall totals were observed at a few locations across the northeastern quarter of the
country, including a statewide 24-hour record of nearly 17 inches at Aurora, IL (just southwest of Chicago) on
July 17-18, and 9 to 13 inches over parts of south-central Pennsylvania and north-central Maryland during
June 18-19. Periodic flooding affected the central Appalachians, the mid-Atlantic Piedmont, and parts of the
Ohio Valley, the Northeast, and southeastern Quebec, according to the NWS Office of Hydrology. More than a
dozen sites along tributaries of the Illinois and Rock Rivers reported record high crests shortly after the mid-July
deluge.
In many of the aforementioned areas, wetness dates back nearly 11 months. During October 1995 - August
1996, most locations from central Ohio, West Virginia, and Virginia northeastward through northern New York
and western Maine and into southern and eastern Quebec reported 125% to 165% of normal precipitation, as did
parts of northern Illinois and peninsular Michigan. Over 60 inches were reported at Elkins, WV during the period
(normal=41.08").
Farther to the west, surplus rains across southern sections of the Intermountain West, Rockies, and Plains
were beneficial, providing significant relief from the drought that affected these regions from late Autumn 1995
through May 1996. Between 15 and 26 inches of rain fell during Summer 1996 across most of Louisiana,
southwestern Arkansas, extreme northeastern Texas, most of Oklahoma, the northeastern Texas Panhandle,
and parts of Kansas and Nebraska. Farther west, 6 to 15 inches of rain fell on much of the Texas and Oklahoma
Panhandles, the central and southern High Plains, and southern and eastern New Mexico. In the latter area,
only 1 to 3 inches of rain were measured through the previous 8 months (October 1995 - May 1996). These totals
represented 150% to 225% of normal in a broad swath from New Mexico eastward across the Texas and Oklahoma
Panhandles and the upper and middle Red River Valley, and through parts of the lower Mississippi Valley and
central Plains (Figure 4).
The persistence of the aforementioned observed anomalies since at least the start of Summer (to as far back
as October 1995 in some instances) can be traced to the persistence of anomalous upper-level ridging and
northward jet-stream displacement across the south-central and western United States while upper-level
troughing and southward jet-stream displacement remained over the East, centered near the Great Lakes (Figure 5). This same general pattern has dominated the United States and southern Canada since October 1995, and
is nearly opposite to the one observed during Summer 1995.
While highs reached 90F on only 10 - 15 days across much of the mid-Atlantic and coastal Carolinas,
typically-mild south-central British Columbia notched 14 - 21 days of 90F+ heat as abnormally warm and dry
conditions dominated much of the West and adjacent Canada (Figure 1). Temperatures averaged 1F to 5F above
normal for the Summer across central and southern Texas, northeastern Mexico, the Southwest, much of the Far
West, the Great Basin, and the Rockies (Figure 2). In addition, Summer precipitation was below 50% of normal in
most of these areas, as well as parts of the northern Intermountain West and Rockies (Figure 4). While drought
relief occurred farther to the north and east, precipitation totals since October 1995 remained under half of
normal across southern Texas, northwestern New Mexico, much of Arizona, parts of northeastern Mexico, the
southern half of Nevada, and interior southern California. Fortunately, water supplies in these areas are
managed by reservoirs that recharge over the course of decades, so that one dry year has minimal impact on water
supplies. Exceptions to this rule included portions of New Mexico, where Summer rains failed to increase low
reservoir levels, and the Rio Grande Valley of extreme southwestern Texas and northeastern Mexico, where river
levels and reservoir stores remain unfavorably low.
The combination of abnormally-high temperatures, little rainfall, "dry" thunderstorms, and occasionally
gusty winds provided ideal wildfire conditions over much of the southern and western United States. Despite
the media attention focused on the cool and wet conditions in the East, the expansive stretches of land charred
by wildfires were more noteworthy. By September 1, 5.67 million acres had been consumed by wildfires across
the 49 continental states since the start of the year, with over 4.41 million acres (78%) located in the Southern,
Southwestern, Great Basin, California, or Northwestern fire regions, according to the National Interagency
Coordination Center. The nationwide total is more than 286% of the average January - August acreage burned
during the previous 5 years (1991 - 1995), and already places 1996 above the other 19 FULL years on record,
surpassing the previous record of just over 5.0 million acres in 1988 [By September 24, the 49-state year-to-date
total had climbed to nearly 5.94 million acres, which was about 269% of the 1991 - 1995 average for the January
1 - September 24 period].