Weather & Natural Hazards

Extreme heat

Missouri summers turn dangerous when heat and humidity stack up. The good news: heat is one of the most preventable hazards there is. Learn the alerts, tell heat exhaustion from heat stroke, and remember the one rule that saves the most lives — never leave anyone in a parked car.

Why it feels worse here

Humidity is the multiplier

Heat is more dangerous in Missouri's humidity, because when the air is muggy your sweat can't evaporate — and evaporating sweat is how your body cools itself. The heat index is how hot it actually FEELS once humidity is added in; the NWS also publishes a HeatRisk scale that shows how risky the next few days are for everyone, not just the most vulnerable.

The alerts

The two heat alerts

A Heat Advisory means use caution. An Extreme Heat Warning means take action — dangerous heat is expected or happening. (The NWS renamed these from 'Excessive Heat' to 'Extreme Heat' in March 2025; there's also an Extreme Heat Watch when dangerous heat is possible.)

Know the difference

Heat exhaustion vs. heat stroke

Heat exhaustion is the warning sign you can usually fix yourself. Heat stroke is a true emergency — learn to tell them apart.

The warning sign

Heat exhaustion

Heat exhaustion comes first, and it's your warning sign: heavy sweating, weakness, dizziness, nausea, headache, and cool, clammy skin. Move the person to a cool place, have them sip water, loosen tight clothing, cool the skin, and rest. Get medical help if they throw up, get worse, or don't feel better within about an hour — heat exhaustion can turn into heat stroke.

Call 911 now

Heat stroke — call 911

Heat stroke is a 911 emergency. The signs are confusion, slurred speech, unusual behavior, a seizure, fainting, a very high body temperature, and very hot skin — and the skin may be DRY or DRENCHED in sweat, so don't wait for sweating to stop. Call 911. While help comes, move the person to a cool place and cool them fast: cool water, wet cloths, ice packs at the neck, armpits, and groin, and fanning. Do NOT give food or drink to anyone who is confused, drowsy, or unconscious.

A car becomes deadly hot in minutes

Never leave anyone in a parked car

Never leave a child, an older adult, or a pet in a parked car — even for 'just a minute,' even with the windows cracked. The inside of a car becomes deadly hot in minutes.

A fan alone may not be enough

Drink water before you feel thirsty. Know that in extreme heat a fan alone may not protect you — once the air is hot enough, a fan just blows hot air and can add heat. Use air conditioning, a cooling center, a library, or a mall instead, and check on the people most at risk.

Working or playing outside

Beat the heat outdoors

Save hard outdoor work for early morning or evening, take frequent shaded breaks, and drink water steadily. (Heading out to hike or work in the heat? The Hiking & Camping hubs cover staying safe in the heat outdoors.)

Heading out in the heat? The Hiking and Camping hubs cover staying safe outdoors when it's dangerously hot.

Make sure the heat alerts will reach you, then build your plan & kit — and on a bad-air day, the air-quality note is here too.

When a warning is issued

Missouri Porch explains the hazard; the National Weather Service and your local officials call the warning.

Last checked: 2026-06-18. Hazards repeat, so most of this page stays true year to year — but alert-product names, the year's stats, and the ShakeOut date can change. Check the date above, and always follow the live National Weather Service warning and your local officials over anything written here.

This site explains and prepares — it is not a live warning. When a warning is issued, follow it and your local emergency officials immediately; they have the live picture. This is not insurance, legal, or medical advice. In any life-threatening emergency, call 911.

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