As we head into the hottest and driest months of the year, it’s a good time to familiarize yourself with words and phrases associated with fire season. Below we try to dispel misconceptions and answer some common questions about hot weather advisories, fire warnings, and smoke event alerts.
What’s the difference between a Fire Weather Watch and a Red Flag Warning?
Both Red Flag Warnings and Fire Weather Watches warn us about critical weather conditions, such as high winds and low humidity or dry lightning, that could lead to increases in wildfire activity. The difference between the two comes down to timing.
A Fire Weather Watch is issued when conditions are expected to occur within a three-day period. But the timeframe for a Red Flag Warning, the highest alert, is much shorter with conditions expected to occur within 24 hours.
What are dry thunderstorms and dry lightning?
Dry thunderstorms typically occur at high altitudes and during hot conditions where most, if not all, precipitation evaporates before reaching the ground. These storms are also likely to create dry lightning, which coupled with hot, dry conditions and increased fire fuels on the ground could spark wildfires.
What are the differences between watches, warnings and advisories when it comes to heat?
Timing, again, is a key difference for heat alerts but this time add a level of certainty and also factor in higher temperatures. A Heat Advisory or Outlook is the lowest alert and means you should prepare for high temperatures within the next 12 hours, but the forecast is unclear just how hot it will get.
Excessive Heat Watches are a notch up from an advisory. Heat watches are issued when conditions are favorable for an excessive heat event, with temperatures reaching into the 80s and 90s during the next 24 to 72 hours.
Excessive Heat Warnings are the highest alerts and are issued within 12 hours of the onset of extremely dangerous heat conditions, with temperatures approaching or exceeding 100 degrees. These warnings could last days or can be downgraded to a watch if dangerous conditions diminish.
Air Quality Advisories vs. Spare the Air.
Both Air Quality Advisories and Spare the Air alerts require you to take precautions, and possibly action to alleviate poor air conditions in the area.
Spare the Air Alerts can be issued because of an unhealthy level of air pollutants such as ozone or fine particles from smoke. If an alert is issued, try to limit outdoor activities. And if the Spare the Air alert is in effect because of fine particle pollution, do not burn wood or other solid fuels in fireplaces, stoves, or outdoor fire pits.
In the Bay Area, when an Air Quality Advisory is issued it’s usually because of a smoke event such as a man-made fire or wildfire. Advisories can be issued even if the local air quality index (AQI) is at normal levels because wildfire smoke can spread rapidly as weather patterns change.
Air Quality Advisories and Spare the Air alerts can often be issued simultaneously or back to back.
To track and learn more about local weather patterns and advisories go here:
- National Weather Service – Bay Area weather and red flag status
For more information on how to protect yourself from heat check out these resources:
- NWS Weather Ready Nation “Beat the Heat” Resources
- CDC Tips for Preventing Heat-Related Illness
- CDC Info for Specific “Heat Sensitive” Groups
- American Red Cross Heat Wave Safety
- Ready.gov Extreme Heat Resource
- OSHA Heat Educational Resources
To learn about air quality and wildfire smoke try these resources:
- Wildfire Smoke and Air Quality at the Lab
- Fire and Smoke Map
- AirNow Air Quality Index
- Purple Air map
- Spare the Air
- AirNow Air Quality Index Basics
More resources and links to consider: