California’s governor has issued a statewide stay at home order in an attempt to stop the spread of COVID-19 in the state after warning that 56% of the population is at risk of getting the coronavirus.

Gov. Gavin Newsom called on all Californians to stay at home, except for essential reasons like buying groceries or seeking medical care.

“We need to bend the curve in the state of California, and in order to do that, we need to recognize the reality, the fact is, the experience we’re having on the ground throughout the state of California… require us to adjust our thinking and to adjust our activities,” Newsom said.

There are 675 confirmed cases of COVID-19 in California and there have been 24 deaths—not counting the Americans who touched down in California on U.S. repatriation flights from abroad. In a letter sent on Wednesday, Newsom warned President Donald Trump that 56% of the population—more than 25 million people—could be infected over the next eight weeks.

The latest measures follow a “safer at home” order by the city of Los Angeles on Thursday and a ‘“shelter in place” order for the San Francisco Bay area on Tuesday.

Here’s what to know about California’s new stay at home order.

When does the ‘stay at home’ order go into effect?

The new measures go into effect on Thursday evening.

Where does this apply?

Residents across the entire state are being asked to stay at home, except for essential purposes.

Some who work in essential state and local government jobs will continue working, including police officers.

How long will it last?

The measures are in force until further notice.

Newsom said at a news conference on Thursday night that the next eight weeks are critical, but didn’t give a timeline for when it would end.

“We could not give you a deadline that we could really believe in,” Newsom said in a press conference. “This is a dynamic situation.”

What’s still open?

Essential services such as gas stations, pharmacies, food stores, banks and laundromats will remain open.

Bars, gyms and other entertainment venues will be closed. Restaurants are closed to dine-in customers.

What can I do?

State officials are asking people to stay home except to get food, care for a relative or friend, get necessary medical care or to go to an essential job.

“I can assure you home isolation is not my preferred choice, I know it’s not yours, but it’s a necessary one,” Newsom said.

Authorities are urging residents to avoid large gatherings, and to stay at least six feet away from other people if they need to leave their homes.

Write to Amy Gunia at amy.gunia@time.com.