SAN DIEGO — Thunderstorms spawned by an influx of monsoonal moisture out of Mexico led to gusty winds and scattered flooding in the eastern reaches of the San Diego area Tuesday as a summer heat wave continued to grip the region.

In the mid-afternoon, inclement conditions that included lightning and heavy showers were moving to the north over state Route 94 and Interstate 8, passing over Boulevard, Jacumba Hot Springs, Pine Valley and other rural areas in the southeastern corner of the county, according to the National Weather Service.

The unsettled atmospheric pattern prompted the federal agency to issue a flash-flood warning for the affected communities, effective through early evening. The alert advises the public to seek shelter in a building or vehicle during electrical storms and to avoid trying to drive over runoff-inundated roadways.

As of 2:45 p.m., up to an inch of rain had fallen in some areas, with in excess of an additional inch expected over the afternoon, the weather service reported.

Among the locales likely to experience flooding and high winds, according to the NWS, were Boulevard; La Posta Indian Reservation; Mount Laguna; Mountain Spring; I-8 between Pine Valley and the Imperial County line; county Highway S1 between Lake Cuyamaca and Mount Laguna; and county Highway S2 between Shelter Valley and Canebrake.

The potential for local thunderstorms will continue through Thursday afternoon in the mountains and deserts, while conditions in the inland valleys are expected to clear up by Thursday, according to meteorologists.

Temperatures will gradually rise through Saturday, when the mercury in the deserts could top out at around 117, forecasters said.