Hilary expected to bring 2 to 3 inches of rain and possible gusts of 39 mph or higher to San Diego coast

Hilary is “highly likely” to impact San Diego as a tropical storm and generate torrential rains that could cause flooding countywide and raise nighttime temperatures into the 80s on the coast, according to the National Weather Service.

Forecasters said Aug. 18 that Hilary — which currently is a Category 4 hurricane off the coast of Mexico — could drop 2 to 3 inches of rain at the coast, 2 to 4 inches in the valleys and 5 to 10 inches in the mountains and deserts.

The outer bands will begin producing rain countywide on Saturday, Aug. 19. The rain will become heavier Sunday, peaking Sunday night and early Monday, when Hilary is expected to arrive in the Southern California region as a tropical storm.

Forecasters say Hilary is likely to pass between the Channel Islands and the California-Arizona border and impact San Diego. It’s possible the system will edge east and flow ashore in Baja California, which would result in less rain on the San Diego County coast but still produce downpours in the eastern half of the county.

“The rain could last for many hours in some places,” said Brandt Maxwell, a weather service forecaster. “And we think there’s a greater than 50 percent chance that tropical storm-force winds will hit coastal waters with gusts of 39 mph or higher.”

Maxwell added that the weather service, for the first time in history, issued a tropical storm watch for San Diego. A flash-flood watch will be in effect for the area from the coast to the inland valleys from late Saturday until Monday night.

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Forecasters said Hilary is so big, and so filled with warm, moist air, that the system could cause temperatures to rise into the 80s at the coast on Saturday night.

San Diego averages only 0.01 inch of rain in August. The most it has ever received during the month is 2.13 inches, which occurred in 1851. “The rain that’s coming will rival that level,” said Adam Roser, a weather service forecaster.

The forecast is based on the latest guidance from the National Hurricane Center, which said Hilary became a Category 4 hurricane late Aug. 17, with sustained winds of 145 mph and periodically higher gusts. The system will lose strength over cooler waters along northern Baja California.

Such storms are quite rare in San Diego. The city has been directly hit by a hurricane only once, Oct. 2, 1858, with winds that gusted upward of 70 mph. San Diego also was directly hit by a tropical storm on Sept. 25, 1939, with winds up to 50 mph.

Tropical Storm Kay last September came within 150 mph of San Diego before it curled off to the west and died. The system produced strong winds and rain in greater San Diego. ◆