Health experts say the county has been in the "high" level of COVID-19 community transmission for more than two weeks.
The CDC recommends wearing a mask in crowded outdoor settings and for activities with close contact with others who are not fully vaccinated in areas with high numbers of COVID-19 cases.
This recommendation does not apply to those actively participating in sports practice, activity or events, whether indoors or outdoors. However, it is recommended when not actively participating, including while on the bench, in locker rooms and riding in team transportation.
Officials say the numbers show the county has spent two straight weeks in the "high" level of transmission with a rising positivity rate of 6%.
The 14-day average positivity rate is 5.2%. This is the first time since early May the metrics are above 5%, which is the rate at which the virus is not suppressed.
Montgomery County also recommends masks be worn in indoor settings, too.
At Valley Forge National Park on Labor Day, people were not wearing masks outdoors but support the guidance.
"I just think if anybody is close to you, you should wear it, even though I'm vaccinated," said Eleanor McDevitt, who strolled on the trail at the historic park.
In Conshohocken at Sutcliffe Park, Anastasia Cooper watched her son and two nieces, all under five years old, and said she could understand the outdoor guidance from both sides.
"I feel like it's fair on both ends. You're outdoors, it's fresh air, so I feel like you're not boxed in," said Cooper.
The county says you should begin wearing a mask Monday if you are not able to stay at least six feet apart from people who do not live in your household while outdoors.
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