A flash flood warning was issued Wednesday for San Bernardino County as July comes to an end with several days of heat, humidity and thunderstorms.
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A strong ridge of high pressure expanding westward over the region will drive temperatures up Wednesday through Friday and draw monsoonal moisture into the region. Some areas might approach excessive-heat levels.
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'It's going to get hot and sunny, and then the thunderstorms come into play later today," said NBC4 forecaster Crystal Egger.
Rain was reported in parts of San Bernardino County at midday. A flash flood warning was issued for the area until 5:30 p.m.
Temperatures started out in the 60s and 70s Wednesday for most of Southern California ahead of some of the summer's warmest days. Showers are possible for inland and mountain areas.
Some coast and coastal valley areas could also see storms later this week. The storms will carry the risk of lightning and flash floods.
Strong rip currents also are expected at Southern California beaches. More than 400 rescues were reported Tuesday at California beaches.
Despite being a typically dry month, this July has been marked by rainfall that has set records. Flash flooding earlier this month washed out a bridge on Interstate 10 near the California-Arizona border, disrupting travel on the major route.
The heat and possible lightning, which can spark fires in dry brush, come during an active wildfire season in California. As of Tuesday morning, nine large wildfires were burning across the state, including the 31,359-acre Lake Fire in San Bernardino County (91 percent contained) and the Wrag Fire in Napa and Solano counties (80 percent contained).
More than 3,890 wildfires have been reported since the start of the year, according to Cal Fire. During that same period last year, 2,757 wildfires were reported across California.
The increase in fire activity occurred during the state's fourth consecutive year of drought, leaving dry vegetation prone to rapid spread of wildfires.