Jacksonville, Fla., which is hosting the celebratory parts of this summer’s Republican National Convention, did an about-face on Monday and mandated the wearing of masks in order to prevent the spread of coronavirus.

The municipal order – which goes into effect at 5 p.m. ET – is for indoor locations and “in other situations where individuals cannot socially distance.” Masks will not be required for most outdoor locations, anyone under 2 years of age or people with breathing problems.

FLORIDA DOCTORS TELL JACKSONVILLE MAYOR HOSTING REPUBLICAN CONVENTION 'MEDICALLY DISRESPECTFUL'

The announcement comes a week after Republican Mayor Lenny Curry of Jacksonville said he didn’t think the need to wear masks was “prudent.” And it comes after Florida’s seen a surge of new coronavirus cases the past couple of weeks.

Hundreds of doctors in Florida sent a letter to Curry and the city council, warning that hosting the convention – which kicks off Aug. 24 – would invite further spread of the coronavirus. The letter says that. with 40,000 people expected to attend, the event should be either "very significantly reduced in numbers" or postponed.

"Allowing this number of people to descend on Jacksonville is unequivocally provocative of disease, predictably harmful, and medically disrespectful to the citizens of this city, much less the rest of the country,” the doctors warned in the letter.

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Earlier this month the Republican National Committee (RNC) chose Jacksonville to host part of this summer’s party convention, after largely abandoning the city of Charlotte, N.C., over disagreements on coronavirus-related crowd restrictions.

President Trump and Republican officials were angered after Gov. Roy Cooper of North Carolina, a Democrat, said he wasn’t prepared to guarantee the RNC a full-fledged convention with an arena packed with party officials, delegates, and activists due to health concerns amid the coronavirus pandemic. While the party will still hold some convention meetings in Charlotte, the major events will take place in Jacksonville.

Fox News' Ronn Blitzer contributed to this report.