Narrative Summary - September 1999

September 1999 was slightly cooler than normal, averaging 65.0ºF, 0.7º below normal
(65.7ºF). The warmest September occurred in 1990 and averaged 72.4ºF, while the
coolest was 58.8ºF in 1985. For calendar year 1999 there were 49 days with maximum
temperatures >= 90ºF compared to a normal of 52 days, and 7 days with maximum
temperatures >= 100ºF compared to a normal of 13 days. The following daily temperature
records were established in September:

                          New          Old
Date   Category          Record       Record     Year
  1    Low Minimum         43           44       1980

No precipitation was recorded during September, tieing the record for the driest September
on record. September 1991 was also totally dry. There have only been 4 months since
recordkeeping began at the Hanford Meteorology Station that have received no
precipitation - August 1955 and 1988, and September 1991 and 1999. The normal
rainfall amount for September is 0.31 in. The wettest September, in 1947, received 1.34
in. Total precipitation since January 1 was 2.94 in., 75% of normal (3.94 in.).

The average wind speed for September 1999 was 7.7 miles per hour (mph), 0.3 mph
above normal (7.4 mph). The windiest September on record averaged 9.2 mph (1961),
while the September with the lightest winds (1957) averaged 5.4 mph. The peak gust for
the month was 42 mph on September 25. The record wind gust for September was 65
mph in 1953.

The monthly climatological data summaries, as well as other information, are available
on the Internet. Address: http://etd.pnl.gov:2080/HMS/. Hanford Site personnel can
access the HMS Intranet site at: http://hms.rl.gov/

The summer of 1999 (June, July and August) was cooler than normal, averaging 72.5ºF, 1.2º
below normal (73.7ºF). The hottest summer, in 1958, averaged 78.2ºF, while the coolest, in
1980, averaged 70.2ºF. The highest temperature was 105ºF on July 28. Precipitation for the
summer season totaled 0.95 in., 115% of normal (0.83 in.). The wettest summer, in 1950,
received 2.99 in., while the driest, in 1973, received only 0.03 in.

For additional information contact:
Ken Burk373-3215
Dana Hoitink372-6414

Note: The information in this summary pertains specifically to
the Hanford Meteorology Station (HMS), which is located
approximately 25 miles northwest of Richland, Washington. No
attempt should be made to infer meteorological conditions at other
locations from these data.