Heat Watch vs. Warning: Do you know the difference?
Published on August 29, 2022
The National Weather Service has issued a heat advisory for our area beginning at 11 a.m., Sunday, Sept. 4, through 8 p.m., Monday, Sept. 5. Please monitor local weather reports for updates and prepare as necessary.
Each National Weather Service Forecast Office issues heat-related information as conditions warrant. National Weather Service local offices often collaborate with local partners to determine when an alert should be issued for a local area. For instance, residents of Southern California are much more prepared for 90°F+ weather than residents in Alaska.
Menlo Park’s local area National Weather Service office is the San Francisco Bay / Monterey, CA office.
Excessive Heat Warning—Take action!
An Excessive Heat Warning is issued within 12 hours of the onset of extremely dangerous heat conditions. The general rule of thumb for this Warning is when the maximum heat index temperature is expected to be 105° or higher for at least 2 days and nighttime air temperatures will not drop below 75°; however, these criteria vary across the country, especially for areas not used to extreme heat conditions. If you don't take precautions immediately when conditions are extreme, you may become seriously ill or even die.
Excessive Heat Watches—Be prepared!
Heat watches are generally issued when conditions are favorable for an excessive heat event in the next 24 to 72 hours. A watch is used when the risk of a heat wave has increased but its occurrence and timing is still uncertain.
Heat Advisory—Take action!
A heat advisory is issued within 12 hours of the onset of extremely dangerous heat conditions. The general rule of thumb for this advisory is when the maximum heat index temperature is expected to be 100° or higher for at least 2 days, and nighttime air temperatures will not drop below 75°; however, these criteria vary across the country, especially for areas that are not used to dangerous heat conditions. Take precautions to avoid heat illness. If you don't take precautions, you may become seriously ill or even die.
Excessive Heat Outlooks—Be Aware!
The outlooks are issued when the potential exists for an excessive heat event in the next 3-7 days. An Outlook provides information to those who need considerable lead-time to prepare for the event.
Heat safety resources
The City of Menlo Park maintains an excessive heat webpage with information on