The city says the mandate is returning because COVID cases have increased 50% over the last two weeks.
PHILADELPHIA (WPVI) -- Starting Monday, masks are now required in all public indoor spaces in Philadelphia as the city moves to Level 2: Mask Precautions under its COVID-19 Response guidelines.
The indoor mask mandate applies to indoor spaces such as restaurants, museums, businesses, offices, government buildings and sports arenas.
The Philadelphia School District was already requiring masks be worn this week following spring break.
The district will now work with the Department of Public Health to determine when to make masks optional again.
Businesses and institutions can go mask-free if they require everyone on-site to be fully vaccinated and check vaccine status upon entry, according to city officials.
The city says the mandate is returning because COVID cases have increased 50% over the last two weeks.
After making the announcement last Monday, the city gave businesses a week to prepare and put signage back up.
A federal judge in Florida struck down the national mask mandate covering airlines and other public transportation Monday. The Biden administration said the rule would not be enforced while federal agencies decide how to respond to the judge's order.
This means masks will not be required on some planes, buses and trains.
SEE ALSO: Lawsuit seeks to overturn Philadelphia's renewed indoor mask mandate
Effective immediately, masks will not be required on SEPTA vehicles and in stations and concourses. In accordance with Philadelphia's mask mandate, all SEPTA employees working inside SEPTA offices, districts and shops within Philadelphia must continue to wear masks until further notice.
The Philadelphia International Airport says masks must still be worn inside terminals. Click here for the latest guidelines from major airlines.
The judge's ruling also means masks are not required on Amtrak.
The city says two of three data points need to be met for the mask mandate to end: new cases must be below 100 per day, cases have increased by less than 50% in the previous 10 days, and hospitalizations are below 50.
As of April 11, Philadelphia was averaging 142 new cases of COVID-19 each day.
"This number is more than 50% higher than the 84 average new cases that was reported ten days ago, on April 1. This means that not only are cases getting higher, they're going up more quickly than the Health Department feels is safe," the Department of Public Health said.
"Hospitalizations have stayed steady around 50 for the last two weeks."
Over the weekend, Philadelphia businesses were gearing up for the major change.
As diners enjoyed their Easter Sunday brunch, restaurants reinstalled signage about requiring masks.
"We definitely do not want any type of shutdown, that's why it's so important for us to stick to the mandates," said Kelsey Nofer, manager at the White Dog Café in University City. "It's just going to be a little bit safer for our guests, anything to keep our guests safe, we're on board with it."
"I support it. I don't feel it's an inconvenience, I feel it's a little safety measure hopefully that will help," added Julie Jacobs, who lives in Rittenhouse Square.
"I think it's bad for businesses, especially the restaurants around here, Rittenhouse Square, Old City, Queen Village restaurants, I mean, they've suffered enough," said John Takacs from Old City.
Dr. Darrn Mareiniss, with Einstein Medical Center, says he believes Philadelphia is doing the right thing.
"I think it's a tough pill to swallow, but I do think Philly is doing the right thing. There's a reason everyone is talking about Philadelphia. And you can say it's a negative, hurting business, but from a public health standpoint I think Philadelphia is acting very responsibly and maturely about this," said Mareiniss.
Lawsuit filed
The mandate is being met with some backlash. A group of about 10 businesses and individuals filed a lawsuit against the city on Saturday, arguing the health department is overreaching.
"It's not only to get some injunctive relief, but the more important issue is to beg a declaratory judgment saying Philadelphia can't engage in this conduct. They do not have the authority," said Thomas Breth, an attorney who is representing the petitioners.
The city says it will not comment on this case, but has the legal authority to do what is necessary to control the spread of COVID-19.
SEE ALSO: Philadelphia reinstates indoor mask mandate as COVID-19 cases rise