San Mateo County moved to the less-restrictive red tier of California's COVID-19 classifications on Tuesday, meaning additional businesses can open.

The county maintained a case rate of less than 7% for the last two weeks, allowing it to move out of the most restrictive purple or "widespread" risk tier to the red or "substantial" risk tier, indicating a lower risk of COVID-19 transmission.

This means restaurants, shopping centers, museums, places of worship, movie theaters and gyms can open indoors with limited capacity. People can visit covid-19.ca.gov/safer-economy and type in "San Mateo County" for specific industry guidelines.

"Hallelujah, we are out of the purple and into the red," San Mateo County Supervisor David Canepa said in a statement. "Now we can eat indoors again, go see a movie and get some exercise at the gym."

"What each and every one of us can do is to commit to patronizing our local businesses," said Warren Slocum, president of the county's Board of Supervisors. "Let's be safe, be healthy and help ensure our small businesses are with us today and tomorrow and the future."

Some businesses like bars, breweries, nightclubs and saunas must remain closed. Schools must continue distance learning and may not reopen fully for in-person instruction until the county has been in the red tier for two weeks.

Fran Dehn, president and CEO of the Menlo Park Chamber of Commerce, said the switch to the red tier provides some relief to some businesses, especially those that weren't able to open for business outdoors. With fall on the way, she added, seasonal changes will make outdoor operations more difficult. Restaurants will now be able to offer patrons more choices based on their safety preferences, whether they want to eat indoors, outdoors or take their food to go, she noted.

Atherton Mayor Rick DeGolia said the new classification is good news, but people should still "be more cautious than ever" this fall since the virus could spread more easily in colder weather.

"The only way that we can avoid slipping back into the purple zone is by wearing masks more and rigorously insuring that we practice social distancing," he said in an email. "The problem is that all we can do is apply a short-term fix, a (Band-Aid), until we have a successful vaccine that is widely accepted and used."

He added that to slow the spread of the virus, more testing needs to be available.

"This is especially important for those who are working in essential services because those people interact with large numbers of others and they can't always be socially distanced," he said. "They need to have readily available tests so that they can avoid going to work whenever they are positive."

Counties are assigned a tier based on test positivity and case rate.

San Mateo County has an adjusted case rate of 6.6 new cases per day per 100,000 people, and a 4.5% testing positivity rate for the week ending Sept. 12. Both numbers are based on a seven-day average with a seven-day lag. The county must continue to have an adjusted case rate below 7% and a testing positivity rate below 8% to remain in the red tier.

"We've increased testing and have seen case rates decline but it doesn't mean this pandemic is over," Canepa said. "We must still practice social distancing, avoid large crowds and most importantly continue to wear our masks."

Social distancing, face coverings and limited gatherings are still enforced under the county's health order.