CHICAGO (CBS) — Storms could put a damper on the festivities at Lollapalooza, as the four-day music festival kicks off on Thursday.

Lollapalooza begins at 11 a.m. at Grant Park, and 400,000 people are expected to attend through Sunday. If you have tickets for Thursday, there’s a chance for storms starting in the afternoon, so you might want to pack a rain jacket or poncho; but, remember, umbrellas are not allowed at the festival.

In case of severe weather, Grant Park might evacuate, and there are three shelters for Lollapalooza visitors: the Grant Park North, Grant Park South, and Millennium Lakeside parking garages. Blue and white signs will point the way to each shelter.

“Everybody’s been trained on how to evacuate this facility, if needed. Their working staff has all been trained on it. The Chicago Police Department, the Fire Department, Office of Emergency Management and Communication (OEMC), we’ve all talked about it, and we’ve drilled this, and we’ve actually did it two times in the past. So if that was to happen, we believe we’re in the best possible position,” said OEMC first deputy director Rich Guidice. “Just as in 2012 and 2015, people who are attending the event can utilize the shelters at Millennium garages. Most of them naturally gravitate to the businesses along Michigan Avenue, but the Millennium garages are our primary shelter location.”

Also, with temperatures expected to reach the mid 80s on Thursday, cooling buses and water stations are available to keep people from getting overheated. Lollapalooza visitors can bring two sealed water bottles to the festival.

As for road closures, Columbus Drive is closed from Monroe Street to Roosevelt Road. Jackson Drive, Congress Parkway, and Balbo Avenue also are closed between Michigan Avenue and Lake Shore Drive.

Pat-downs and bag searches will be conducted at all Lollapalooza entrances.

Chicago police are adding more officers downtown for the festival Lollapalooza also has hired its own security guards.