San Diego could reach nearly 100 degrees as a long heat wave settles over the county

San Diego County will be hit by a potentially “dangerous” heat wave that will begin on Tuesday and last through Labor Day, with some of the worst conditions coming on Saturday, when San Diego State University plays its first football game at recently completed Snapdragon Stadium in Mission Valley.

The National Weather Service has issued an excessive heat watch that will go into effect Tuesday morning and last at least until Sunday night, and likely through next Monday, when the Padres begin a home stadium at Petco Park on Sept. 5.

Temperatures will begin to rise on Tuesday when a huge dome of high pressure starts to develop over central Nevada. Forecasters say the dome will settle in and get bigger, causing temperatures to jump 6 to 12 degrees above normal in many areas Wednesday through Sunday.

The heat will likely range from 95 to 105 degrees during that period in such areas as Valley Center, Escondido, Ramona, Poway, Alpine and Jamul, the weather service says. Coastal cities will be in the 80s, the mountains could hit the 90s, and the deserts will be 110 to 115 degrees.

“We’re going to have very high daytime temperatures, warm nights, and this will be a long duration event, so it could be hard on people with certain medical conditions,” said Mark Moede, a weather service forecaster.

“The temperature will be near 90 during (Saturday’s Aztec game at Snapdragon), which will be hard not only on players and coaches, but on fans.”

SDSU will face off against Arizona starting at 12:30 p.m.

Winds are expected to be light, which will help reduce the risk of wildfires in a county that’s in the midst of a drought. But Moede says it’s possible that the seasonal monsoon will surge back to life on Thursday and last several days, producing high humidity from the coast to the mountains.

The heat wave will affect all of Southern California, which means that it is possible that the California Independent System Operator, the primary operator of the state’s electric power grid, will issue one or more Flex Alerts, asking consumers to reduce power consumption during certain times of the day.