The weather is one of the biggest predictors of crowd size at the Grand Prix, the city’s largest event of the year.

And after a mid-week heat wave expected to last through today, attendees to the Downtown event this weekend will likely see mild temperatures and sunny skies.

Temperatures will sink back to the mid-70s Friday, Saturday and Sunday, with patchy fog in the morning and partly-cloudy skies.

The National Weather Service said there is, however, a 20% chance of thunderstorms on Friday. On Sunday, the day of the IndyCar race, forecasters predict a temperature of 74 degrees.

The warm, dry temperatures began Tuesday, with a high of 93 degrees expected today. On Thursday, the temperature is expected to drop significantly to 78 degrees.

The National Weather Service issued a heat advisory through 8 p.m. today for San Fernando Valley, where temperatures of up to 105 degrees were expected.

An onshore flow was expected to begin later today, significantly cooling temperatures through the weekend.