California may be experiencing its worst drought ever, but a brief outburst of rain on Tuesday made August seem almost torrential.
More than a half-inch of the wet stuff fell in Concord and other spots east of the Caldecott Tunnel on Tuesday morning, and wet roads, gray skies and steady showers greeted early risers in the East Bay. Forecasters said nothing was surprising about it -- the high low-pressure system that produced the rain had been expected to blow up from Southern California -- until one considers the calendar.
"It's definitely not what you expect to see this time of year," National Weather Service senior forecaster Logan Johnson said. "August is usually very dry. But we'll certainly take it. Any rain we get we'll take, obviously."
Any rain in August usually constitutes a bonus, NWS forecasters said. The average August rainfall in Concord, where .07 inches fell Tuesday, is only .03 inches a month, a figure that is high among most Bay Area communities, forecaster Steve Anderson said.
"Rain in August is not something we see very much," he said.
The rain stayed mostly in the North Bay near Napa and touched areas of the East Bay, as well. The first rain began falling sometime around 2 a.m., with some of the heavier stuff around 4 a.m., according to the NWS.
The .07 inches recorded at Concord's Buchanan Field Airport and at Napa County Airport were the most reported overnight, forecaster Logan Johnson said.
The system did not extend to San Francisco or the South Bay, Johnson said, with no rain falling in cities in Santa Clara and San Mateo counties.
The system was typical of those that form in Arizona, southern Nevada and Southern California during the late-summer monsoon season, Johnson said. Generally, such systems don't reach the Bay Area, but Johnson said the low barometric pressure in the upper levels of the atmosphere pulled this particular system north.
"It happens once in a while," he said.
The wet stuff was not expected to last more than a day, Anderson said. Clouds were expected to depart overnight into Wednesday, Anderson said.
"They'll be replaced by the same high-pressure, sunny, warm weather that we usually see," he said.
Still, the temperatures were expected to be mild through the weekend, Anderson said, with the thermometer expected to be in the mid-80s and lower throughout the Bay Area.
Contact Rick Hurd at 925-945-4789 and follow him at Twitter.com/3rderh.