Not your typical
long, hot summer
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[SEPT. 3, 2004]
you think that the weather in Illinois this summer has been cool and
wet, you're right; but these conditions are not unique to Illinois,"
said Jim Angel, state climatologist. "Temperatures this summer in
most of the eastern two-thirds of the United States also have been
cooler than normal, as frequent intrusions of Canadian air have
dominated the region. By contrast, warmer than normal temperatures
have affected the northwestern United States."
Angel is associated with the
Illinois State Water Survey, a
division of the Illinois Department of Natural Resources
"While the magnitude of the cool
temperatures this year has been extraordinary, the pattern is not
unique to 2004," he said. "Following a period of frequently very hot
summers in the 1930s and early 1950s, the period since the late
1950s has seen relatively cool summers on average in Illinois, with
no trend over that period. At the same time, summers in the western
United States have become progressively hotter.
"This regional difference in trends is
probably caused in large part by a change in the overall atmospheric
circulation patterns. The ultimate causes of these shifts are not
clear at this time.
"Temperatures in Illinois this summer
are averaging 3.1 degrees below normal statewide, with even colder
August temperatures, 4.9 degrees below normal. Both summer and
August rank as the fifth coldest since 1895. In recent years, only
1992 was ranked colder -- [the] third coldest summer and August
since 1895. The 1915 record still stands for the coldest summer, 3.9
degrees below normal, and coldest August, 5.8 degrees below normal."
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column in this article]
Temperatures this August are averaging
68.7 degrees, with precipitation averaging 5.45 inches, 149 percent
of normal. Temperature extremes this month have ranged from 40
degrees at Congerville on Aug. 15 to 97 degrees at Kaskaskia on Aug.
19. Grayville reported the largest one-day precipitation total: 6.87
inches on Aug. 26.
"June-August temperatures are averaging
only 70.7 degrees, and precipitation is averaging 12.87 inches, 111
percent of normal," Angel said.
Although the National Weather Service
is calling for an increased chance of cooler than normal
temperatures for September, the temperature outlook for
November-January is neutral, suggesting a return to more seasonable
"The type of
summer we're having this year does not necessarily foreshadow an
early frost," Angel said. "For example, an analysis of the 10
coldest summers in Champaign-Urbana yields a first fall frost date
only six days earlier than the 1971-2000 average of Oct. 17. The
first frost typically occurs on Oct. 7-14 (northern Illinois) and
Oct. 14–21 (central and southern Illinois)."
from Eva Kingston, editor,
Illinois State Water Survey]