A heat wave is a period of abnormally hot weather generally lasting more than two days. Heatwaves can occur with or without high humidity. They have potential to cover a large area, exposing a high number of people to hazardous heat.
Never, never leave children, disabled or elderly adults, or pets in parked, unattended vehicles. Studies have shown that the temperature inside a parked vehicle can rapidly rise to dangerous levels for people and pets. Leaving the windows slightly open does not significantly decrease the heating rate. The effects can be more severe on children because their bodies have not developed the ability to efficiently regulate internal temperature.
It is important to know the difference between a Heat Watch and a Heat Warning. Each National Weather Service Forecast Office issues some or all of the following heat-related products as conditions warrant. NWS local offices often collaborate with local partners to determine when an alert should be issued for a local area. For instance, residents of Florida are much more prepared for 90°F+ weather than residents in Alaska.
- Excessive Heat Warning: 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 night time 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: Heat watches are 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: 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 night time 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.
The National Weather Service has multiple tools to assess the potential for heat stress due to extreme temperatures. One such item is the Heat Index. The Heat Index is a measure of how hot it really feels when relative humidity is factored in with the actual air temperature.
Hot temperatures does not mean warm waters. River and lakes can still be cold so please wear a lifejacket.
In summary, be safe when going outdoors in hot weather. When it is hot, wear lightweight, loose-fitting and light-colored clothing. Hats are also a good idea to protect your face and scalp from harmful UV rays if you will be spending time directly in the sunshine. Apply sunscreen liberally. Drink plenty of non-alcoholic and non-caffeinated beverages. When going out to the river or lake wear a lifejacket.