Page created and maintained by Roger Edwards, Storm Prediction Center
During the summer and early fall of 2000, much of north Texas and Oklahoma endured the most intense dry period ever recorded in the region. Oklahoma City went 54 consecutive days without measurable rainfall. At Dallas/Fort Worth, not a single drop of rain fell in the airport gauge for 84 days in a row -- shattering the old record of 58 straight rainless days there. The combination of the longest dry spell on record and daytime temperatures commonly in the 90s and low 100s F caused soil temperatures to soar well into the 90s and low 100s as well, according to readings from Oklahoma mesonet sites.
Significant rains finally came to a narrow swath of this parched region (above) on the night of September 22-23, moistening the ground. A band of thunderstorms from northwest Texas across central Oklahoma dumped up to 4 inches of rain, based on radar measurements and gauge-biased radar totals. A look at 60-day rainfall totals (as a percent of normal) shows many surrounding areas got no rain at all.
This left a corresponding swath of soil which was cooler during the day -- as shown by the black and gray area in the infrared image above -- and warmer at night. Water gains and loses heat much more slowly than air; so when water replaces air in previously dry soil, the wet ground takes on the same tendency. An infrared satellite image with overlaid surface observations shows not only the cooled ground (gray areas), but the cooler daytime temperatures (red numbers) and warmer dew points (green numbers). For several days after the rain event, the ground added moisture to the air above it so strongly that it could be detected in surface weather stations.