Tens of thousands of football fans have crowded into Levi's Stadium in recent weeks for the first couple 49ers preseason games with no vaccine mandate — though masks are required in indoor spaces. But BottleRock Napa Valley, happening over Labor Day Weekend, will be the first big test for the region when it comes to hosting a large-scale, non-seated music festival in the time of COVID.

BottleRock has been postponed several times since its original postponement — now in its eighth iteration after taking 2020 off, it typically takes place over Memorial Day weekend in May. But it's full steam ahead for Friday, with another 100,000 or more attendees expected. The festival was fully sold out as of last month, and the 2019 edition of BottleRock saw more than 120,000 people stream through the downtown Napa area. (If you're still looking for tickets, or looking to offload some, you can do so on the official ticket exchange.)

The Delta variant surge prompted one headliner, Stevie Nicks, to back out several weeks ago out of caution and fears for her health — she's also canceling the remainder of her tour dates this year. And as KRON4 reports, the surge and the coming crowds have some locals nervous as well.

The festival is requiring proof of vaccination (or a recent negative COVID test), encouraging mask-wearing outdoors, and requiring masks in enclosed spaces — but all that may not be enough to fully prevent any spread of the contagious virus variant. Also, there will be a pop-up COVID-testing tent outside the festival (750 3rd Street in Napa) from 9 a.m. to 9 p.m. on Thursday, for those who want to pay for a rapid test prior to attending Friday — if you make an appointment it will cost you $79, but if you just walk in it will be $89.

"I’ve kind of thought this whole time because I’m vaccinated, I’m okay and I’m not going to hurt kids or someone who can’t get vaccinated, I can’t give it to them but I can be carrying it and that’s frightening," says Napa resident Shannon Anthony, speaking to KRON4. Anthony doesn't feel like the vaccination requirement should be any reason to worry less about the crowds.

Still, Lollapalooza managed to happen in Chicago in late July, amid surging COVID cases, and reportedly out of more than 385,000 attendees, less than 0.05% ended up with a COVID infection. That figure was cited in a statement by Napa County Public Health Officer Dr. Karen Relucio.

"BottleRock is requiring proof of vaccination of all attendees and staff or a negative COVID test 72 hours prior to attendance, indoor mask use is mandatory, and they are highly recommending outdoor mask use. These measures were successful at markedly decreasing transmission during the Lollapalooza music festival in," Relucio says.

Another outdoor music festival in the Netherlands in early July led to over 1,000 documented COVID cases despite a negative-test requirement at the gates — and with around 20,000 attendees, that is an infection rate of 5%, though it's not known what percentage of the attendees were fully vaccinated.

Organizers of Outside Lands, now scheduled to happen in San Francisco's Golden Gate Park over Halloween weekend, will no doubt be watching closely how BottleRock plays out, and whether any outbreak of cases is detected afterward.

Related: Nine Takeaways From BottleRock 2019

Photo courtesy of BottleRock