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San Francisco Health Network

FAQ: Extreme Weather during COVID-19

Last updated on July 9, 2021

Safer Return Together

On January 10, 2022, Health Order C19-07y was updated to align with new changes from the State of California around Mega-Events thresholds and requirements; and added recommendation to wear higher-quality masks and recommendation for children in schools be up-to-date on vaccination.  The previous revision temporarily suspending certain exemptions to the indoor universal mask requirement remains in effect until February 1, 2022. A Redline is available. C19-07y will continue until amended or rescinded by the Health Officer. Please see the FAQ for more information on C19-07y.

Note: On June 15, 2021, the California Blueprint for a Safer Economy was replaced by statewide COVID-19 guidance for certain settings. The San Francisco Health Officer's declaration of a health emergency arising from the pandemic continues to be in effect.

Background: COVID-19 is transmitted more easily indoors than outdoors, but when the San Francisco Bay Area is impacted by wildfires and extreme heat, people may be advised to go indoors to protect against health effects from smoke, ash, or heat. This FAQ describes some steps you should consider when there is wildfire smoke and/or extreme heat during the COVID-19 pandemic.

Vaccines: COVID-19 vaccines are effective at protecting you from getting sick even after you have had COVID-19. Vaccination is an important tool to help us get back to normal.

Extreme Heat

Extreme heat can be dangerous, particularly for older adults. Exposure to extreme heat can cause general fatigue, worsening of underlying health conditions, and/or lead to life-threatening heat stroke. People who live in San Francisco may be at higher risk from extreme heat because San Francisco is typically cool, and people have not had a chance to adapt to higher temperatures. Additionally, many people in San Francisco do not have access to air conditioning in their homes.

To protect yourself from extreme heat, follow the guidance at Visiting a cooling site is an important option.

How can I keep myself safer from COVID-19 when visiting a cooling site?

  • Get vaccinated for COVID-19
  • Follow all requirements and recommendations regarding wearing face coverings in the cooling site and while taking public or shared transportation.
  • Unvaccinated individuals should stay 6 feet apart from people outside your household.
  • Visit a site with a fully functioning HVAC.

Can I visit the cooling site if I am positive for COVID-19?

No. If you are Isolating due to COVID-19 and experience illness due to heat, please seek medical attention. If you do not have a place to safely Isolate you may be able to ask a medical provider for a referral to an Isolation and Quarantine Hotel.



Smoke and ash from wildfires can irritate your eyes, nose, throat, and lungs, and increase your chances of developing a respiratory infection such as pneumonia. Wildfire smoke may also worsen illness from COVID-19.

Why is staying indoors an effective way to protect myself from wildfire smoke during the COVID-19 pandemic?

The most effective way to protect yourself from wildfire smoke is to stay indoors or limit your time outdoors when there is smoke in the air. This is especially important if you have heart or lung disease or are at higher risk for adverse health effects. Staying at home also reduces your exposure to COVID-19.

How can I make my indoor space safer to prevent risk of COVID-19?

You can create a cleaner air space at home by closing all windows and doors and running fans or air conditioning with a new filter on recirculate to prevent outside air from coming inside. If you have one, use a portable air cleaner to filter the air in the rooms you occupy most. To keep the indoor air clean, avoid activities such as burning candles, using gas stoves, and vacuuming.

How do I know if I should wear a mask outdoors during a wildfire event?

You can monitor the air quality at and follow the guidelines in the table (page 4) from the California Air Resources Board.

Will my cloth or fabric face coverings protect me from wildfire smoke?

Cloth or fabric face coverings are useful to prevent transmission of COVID-19 because they block the large particles or droplets that may carry coronavirus. These types of face coverings do not filter out the tiny particles that cause respiratory problems during wildfire events.  If you have an N95 or P100 respirator (mask) available, consider wearing it when you go outside. Respirators can filter out small airborne particles produced from fires.

I thought we weren't supposed to use N95 respirators because there was a shortage. Are N95s now available?

There is no longer a shortage of N95 respirators in the United States. Respirators can be found online, or in hardware, home repair, or drugstores. People with heart or lung problems should check with their healthcare provider before using a respirator because the respirator can make it more difficult to breathe. Respirators are not designed to fit children.

How do I use a respirator if I have one?

SFDPH has prepared some tips for wearing an N95/P100 respirator. Follow the mask manufacturer’s instructions. Try to seal the mask closely to your face. As a good seal is not possible with facial hair, make sure the skin is clean shaven where the respirator touches the face. Throw away your respirator when it gets harder to breathe through or if it gets dirty.

If you have difficulty breathing, get dizzy, or have other symptoms while wearing a respirator, go to a place with cleaner air and remove it. Wearing a respirator, especially if it’s hot or you are physically active, can increase the risk of heat-related illness. Take breaks often and drink water.

Can I wear an N95 respirator with a one-way valve?

Masks with one-way valves (often a raised plastic disk about the size of a quarter, on the front or side of the mask) do not protect others from COVID-19, as they can expose other people nearby to air you exhale. If masks are recommended or required for COVID-19 prevention (such as in transit or healthcare facilities, or if you are unvaccinated), you can wear a cloth face covering or simple face mask over a respirator with a valve.

Do KN95 masks protect against wildfire smoke?

KN95 masks that have been approved by National Institute for Occupational Safety and Health (NIOSH) are equivalent to N95s. Be sure that your KN95 is approved -- on July 6, 2021, the FDA revoked the Emergency Use Authorization of non-NIOSH approved respirators because the supply of NIOSH approved respirators had recovered in the U.S.

How can I keep myself safer from COVID-19 when visiting a cleaner air site?

  • Get vaccinated for COVID-19
  • Follow the current health order regarding wearing face coverings.
  • Unvaccinated individuals should stay 6 feet apart from people outside your household.
  • Visit a site with a fully functioning HVAC.

EPA Air Quality Index and Actions You Can Take to Protect Yourself

EPA Air Quality Index and Actions for Sensitive Groups