DesertWeather.com blog

On this day in…
2004: Severe thunderstorms in Borrego Springs produced one inch hail that broke windows. Strong winds gusted to 60 mph before the anemometer was destroyed, and knocked down six power poles. Training thunderstorms over Johnson Valley produced severe flash flooding. Hwy. 247 was washed out in numerous sections. Minor damage to homes occurred and 12 vehicles were trapped. In La Quinta, 138 trees were knocked down at one golf course with damage to a building. More trees fell down at other golf courses. Roof tiles were blown off. Damage occurred to power poles and transformers.
1990: It was 117° in Borrego Springs, the highest temperature on record for September. This also occurred the previous day on 9.10.
1976: Record rains that started on 9.9 ended on 9.12 came from Tropical Storm Kathleen (called a 160+ year event by meteorologists). 14.76 inches fell on south slopes of Mt. San Gorgonio, 10.13 inches at Mt. Laguna, eight inches at Mt. San Jacinto, four+ inches in the Little San Bernardino Mountains, and 1.8 to 2.8 inches in the Coachella Valley. Deep Canyon (above La Quinta) recorded 2.96 inches in three hours on 9.10. Rainfall in the Santa Rosa Mountains above the Coachella Valley was called the heaviest in recorded history. Six were buried and killed in sand in Ocotillo. Floods of record were attained at numerous streams around the Coachella Valley. 1.84 inches of rain fell in Riverside on this day, 2.09 inches fell in Borrego Springs, 2.33 inches fell in Victorville, 2.57 inches fell in Idyllwild, and five inches fell in Palomar Mountain, each the greatest daily amounts on record for September. The Victorville amount is also the third highest daily amount on record. This occurred during the El Nino of 1976-77. Hurricane Kathleen also brought the southwest the highest sustained winds ever associated with an eastern Pacific tropical cyclone with sustained winds of 57 mph at Yuma on 9.10.

On this day in…
2004: Thunderstorms in Borrego Palm Canyon produced a wall of mud eight to ten feet high and 150 yards wide. Severe flash flooding occurred. In Borrego Springs 70-90 homes were damaged and a campground was washed out.
1990: It was 117° in Borrego Springs, the highest temperature on record for September. This also occurred the next day on 9.11.
1977: Heavy rains in Little San Bernardino Mountains (Joshua Tree NP) produced a rainfall of nearly five inches in one hour above the Thousand Palms Wash. Flash floods down Thousand Palms Wash caused extensive damage to Thousand Palms area, nearly destroying the oasis in the valley. The California Aqueduct that runs just north of the preserve was clogged with debris, resulting in the flood of nearly a billion gallons of water through this area.
1976: Record rains that started on 9.9 ended on 9.12 came from Tropical Storm Kathleen (called a 160+ year event by meteorologists). 14.76 inches fell on south slopes of Mt. San Gorgonio, 10.13 inches at Mt. Laguna, eight inches at Mt. San Jacinto, four+ inches in the Little San Bernardino Mountains, and 1.8 to 2.8 inches in the Coachella Valley. Deep Canyon (above La Quinta) recorded 2.96 inches in three hours on this day. Rainfall in the Santa Rosa Mountains above the Coachella Valley was called the “heaviest in recorded history.” Six were buried and killed in sand in Ocotillo. Floods of record were attained at numerous streams around the Coachella Valley. 1.41 inches of rain fell in Santa Ana on this day, the only occurrence of precipitation for this day on record. 2.76 inches fell in Palm Springs and 2.34 inches fell in Big Bear Lake, each the greatest daily amount on record for September. On this day 2.8 inches fell in 3 hours in Borrego Valley and 1.74 inches fell this day in LA, a daily record. This occurred during the El Niño of 1976-77. Hurricane Kathleen also brought the southwest the highest sustained winds ever associated with an eastern Pacific tropical cyclone with sustained winds of 57 mph at Yuma on this day. The Padres’ home game against the Houston Astros was rained out at (then) San Diego Stadium. This is the only rainout to have occurred during September in Padres history (since 1969).
1960: North northwestward moving Hurricane Estelle dissipated west of the central Baja California coast. The heaviest rains were over the San Diego County Mountains with 3.40 inches recorded at Julian over 9.9 and this day.
1945: A tropical cyclone moving north northwestward just off the west coast of Baja California dissipated off the coast of northern Baja California. Showers produced rainfall up to two inches in the mountains over 9.9 and this day.

Note the drop in surface Dew Point levels this evening around 9pm. The winds reversed from the southeast to the Northwest helping in the dry out!

Dew Point (Blue) Wind Dir (red)

On this day in…
2006: Heavy thunderstorms occurred along the Elsinore Convergence Zone near Hemet. Roads closed in Hemet, cars were stalled, a mudslide along Hwy. 74. The thunderstorms also produced strong winds estimated at 70 mph. Damage was done to trees, buildings, and power lines from San Jacinto to Temecula. There was also extensive damage to local wineries.
1978: Hurricane Norman recurved with the remnants tracking into southern California from the south southwest. Rainfall exceeded three inches in the mountains on 9.5 and on this day. This occurred during the El Niño of 1977-78.
1972: Hurricane Hyacinth moved as far west as 125 West before recurving to the northeast. The remnants made landfall between Los Angeles and San Diego on 9.3 with winds of 25 mph and rainfall of up to one inch in the mountains from 8.29 to this day. This tropical cyclone holds the distinction of traveling the farthest west before recurving and making landfall in Southern California. This occurred during the El Niño of 1972-73. Only 0.44 inch was measured in San Diego.
1939: The remnants of a hurricane tracked northeastward across northern Baja California into southwest Arizona starting on 9.4 and ending on this day. Up to seven inches of rain fell on the mountains and deserts. Blythe received more rain than would normally fall in a year and Imperial received more rain than would normally fall in two years. Four tropical cyclones would impact Southern California during the month of September 1939, an unprecedented occurrence. 1.21 inches fell in San Diego. Floods through eastern canyons inundated Thermal with three feet of water. Extensive damage occurred in Mecca.

The cooling of the air by the Thunderstorms to our south and the outflow winds that blew north brought us a sharp drop in temperatures by about 12 degrees in one half hour! Although we saw no rain we did benefit from it down south.

Below is a graph showing the sharp drop in temperature around 6:15pm.

Temperature Drop