What is the difference between a Heat Advisory and an Extreme Heat Warning?

A Heat Advisory is the lower tier — issued for hot, uncomfortable conditions that are risky mainly for vulnerable people. An Extreme Heat Warning (formerly called an "Excessive Heat Warning") is the serious tier — dangerous, potentially life-threatening heat that is expected or already happening, where everyone should take action. The dividing line is the heat index, with exact thresholds set by each local NWS office.

What is the difference between an Extreme Heat Watch and an Extreme Heat Warning?

An Extreme Heat Watch means dangerous heat is possible in the next day or two — prepare. An Extreme Heat Warning means that dangerous heat is expected or happening now, so you should take action to stay cool and hydrated immediately.

Why did the name change from "Excessive Heat Warning"?

The National Weather Service updated its heat products to use clearer wording. "Extreme Heat Warning" and "Extreme Heat Watch" replace the older "Excessive Heat" names, and "Heat Advisory" covers less severe but still notable heat. The meaning of each tier is unchanged.

What is the heat index?

The heat index, or "feels-like" temperature, combines air temperature and humidity to estimate how hot it actually feels to your body. High humidity stops sweat from evaporating, so a 95°F day at high humidity can feel well over 105°F — which is why alerts are based on the heat index, not just the thermometer.

Weather Alerts

What Is an Extreme Heat Warning?

LK Forge · 5 min read · Updated June 2026

An Extreme Heat Warning means a period of dangerously hot weather is happening or about to, and it is serious enough to threaten health — even for healthy people without relief from cooling and hydration. Heat is, on average, one of the deadliest forms of weather in the United States, which is why these alerts matter.

Warning vs Watch vs Advisory

Heat Advisory — hot conditions that are uncomfortable and risky for vulnerable people. Take it seriously, but it is below the "extreme" threshold.
Extreme Heat Watch — dangerous heat is possible in the next day or two. Make a plan to stay cool while it is easy.
Extreme Heat Warning — that dangerous heat is now expected or underway. Act to protect yourself and others now.

If those tiers are new to you, start with watch vs warning vs advisory.

A note on the name

You may still see the older term Excessive Heat Warning. The NWS modernized its wording so the alerts read more plainly: Extreme Heat Warning and Extreme Heat Watch now carry the most serious heat messages, with Heat Advisory for lesser events. The thresholds and meaning are the same — only the labels are clearer.

Why it's about the heat index, not just the temperature

Heat alerts are triggered by the heat index — the "feels-like" temperature that blends air temperature with humidity. When humidity is high, sweat cannot evaporate to cool you, so the body struggles. That is why a 95°F afternoon can carry an Extreme Heat Warning in a humid climate but only a Heat Advisory, or nothing, in a dry one. Work out the heat index for any temperature and humidity with our calculator.

How to stay safe

Get to air conditioning — your home, a friend's, a library, mall, or a public cooling center.
Hydrate with water; skip alcohol and sugary drinks. Don't wait until you're thirsty.
Never leave children or pets in a parked car — interior temperatures climb to deadly levels within minutes.
Check on others — older adults, people who are ill, and anyone without air conditioning are most at risk.
Know the warning signs of heat exhaustion and heat stroke (confusion, hot dry skin, fainting) and call for help immediately if they appear.

Check your area

See whether an Extreme Heat Warning, Watch or Advisory is active where you are with the free Weather Alerts tool. In dry, windy heat, also watch for a Red Flag Warning for fire danger.

Check whether an Extreme Heat Warning or Watch is active for your location.

Open the Weather Alerts tool

Frequently asked questions

What is the difference between a Heat Advisory and an Extreme Heat Warning?: A Heat Advisory is the lower tier — issued for hot, uncomfortable conditions that are risky mainly for vulnerable people. An Extreme Heat Warning (formerly called an "Excessive Heat Warning") is the serious tier — dangerous, potentially life-threatening heat that is expected or already happening, where everyone should take action. The dividing line is the heat index, with exact thresholds set by each local NWS office.
What is the difference between an Extreme Heat Watch and an Extreme Heat Warning?: An Extreme Heat Watch means dangerous heat is possible in the next day or two — prepare. An Extreme Heat Warning means that dangerous heat is expected or happening now, so you should take action to stay cool and hydrated immediately.
Why did the name change from "Excessive Heat Warning"?: The National Weather Service updated its heat products to use clearer wording. "Extreme Heat Warning" and "Extreme Heat Watch" replace the older "Excessive Heat" names, and "Heat Advisory" covers less severe but still notable heat. The meaning of each tier is unchanged.
What is the heat index?: The heat index, or "feels-like" temperature, combines air temperature and humidity to estimate how hot it actually feels to your body. High humidity stops sweat from evaporating, so a 95°F day at high humidity can feel well over 105°F — which is why alerts are based on the heat index, not just the thermometer.