The World Health Organization (WHO) updated its global heat fact sheet on July 31, 2026, saying deaths and hospitalizations linked to extreme heat can occur on the day of an event and in the days immediately after it. The short interval makes official warnings a prompt for action before symptoms appear.

A household plan should connect each local warning to a decision: move an activity, shorten time outdoors, identify a cool place or check on someone who may need help. Emergency symptoms require a separate response and should not wait for an alert level to rise.

Confusion, seizures or collapse require emergency help

The US National Institute for Occupational Safety and Health (NIOSH) lists confusion, altered mental status, slurred speech, seizures and loss of consciousness as signs of heatstroke, which can be fatal if treatment is delayed. Hot, dry skin is one possible sign, but profuse sweating can also occur, so continued sweating does not rule out heatstroke.

Call the local emergency medical service, move the person to shade or a cool indoor place, remove outer clothing and begin cooling while help is on the way. NIOSH advises wetting the skin or clothing, applying cold wet cloths and moving air around the person while someone stays with them until emergency responders arrive.

Headache, nausea, dizziness, weakness, intense thirst and heavy sweating may accompany heat exhaustion. WHO advises moving to a cool place and drinking water when the person is alert, while persistent unusual symptoms or heat cramps lasting more than one hour need medical attention.

Use the local warning rather than a universal cutoff

WHO defines a heatwave through excess heat under local conditions and advises the public to stay informed about official heat warnings. A color category or temperature threshold from one country should not be substituted for the alert issued by the national or local authority where the activity will occur.

Check the forecast for the place and time of the planned activity, including the overnight period if the home stays hot. A lower alert category is not a guarantee of safety because risk also depends on exposure, physical effort, clothing, health, age and access to cooling.

Assign one person to check the warning before departure and another to confirm that water, shade and a cool retreat are available. The plan should also state which alert or condition will shorten, move or cancel an activity, using local health and weather advice.

Cooling, water and rest work as a package

WHO advises staying out of the heat during the hottest time of day, using shade, moving to the coolest room, taking cool showers or baths, wetting the skin and drinking water regularly. Cooling reduces heat gain, rest reduces heat produced by activity and water replaces part of what is lost through sweating.

This report does not set one daily fluid volume for every person. People whose clinician has limited their fluids, or who have heart or kidney conditions, need a plan matched to their condition rather than a generic cup count.

Ventilation also depends on the temperature difference between indoors and outdoors. WHO advises opening windows after dark only when outdoor air is cooler, blocking direct sunlight when it is hotter outside and using electric fans only below 40 degrees Celsius because hotter air can heat the body.

Children and older adults need earlier planning

Infants and children

Children depend on adults to change the route, activity and cooling arrangements before heat becomes a problem. WHO says children should never be left in a parked vehicle for any amount of time and should avoid direct sun during peak hours.

A caregiver should know where the child can cool down and should watch for unusual behavior, weakness or reduced responsiveness. Confusion, a seizure, collapse or loss of consciousness requires the emergency response described above.

Older adults

The US Centers for Disease Control and Prevention (CDC) says adults aged 65 and older may adjust less well to sudden temperature changes and are more likely to have chronic conditions or take medicines that affect temperature control or sweating. The agency advises staying cool and hydrated and arranging check-ins rather than assuming the person will ask for help.

The check-in plan should confirm access to a cool place, fluids and a working way to call for assistance. People with clinician-set fluid limits should ask how those limits apply during hot weather instead of increasing intake on their own.

Pregnancy

WHO's European office says the effects of heat in pregnancy depend on the frequency, intensity and duration of exposure and advises moving activity or travel to cooler conditions where possible. It also says reduced fetal movement is a reason to contact a midwife or pregnancy care provider, during a heatwave or at any other time.

Chronic conditions and medicines change the plan

WHO says heat places extra strain on the heart and kidneys and can worsen risks linked to cardiovascular, respiratory, mental health and diabetes-related conditions. The relevant trigger is therefore the person's condition and exposure alongside the official warning, not the air temperature alone.

US CDC clinician guidance says its recommendations reflect expert opinion, lists diuretics, anticholinergic drugs and some psychiatric medicines as potential heat-risk factors, and calls for individualized review before changing a dose, schedule or fluid restriction. Regular medicine should not be stopped or changed solely because a hot day is forecast.

A heat plan for someone with chronic illness can cover access to cooling, the permitted fluid range, medicine storage and whom to contact if symptoms develop. That plan is best settled with the treating clinician before a heat alert rather than improvised during one.

Work and sport need controlled exposure

US NIOSH workplace guidance calls for limiting time in heat, increasing recovery time in a cool area, providing drinking water, using a buddy system and activating a heat-alert program when the weather service forecasts a heatwave. Employers remain responsible for the rules and emergency procedures that apply in the country and workplace concerned.

NIOSH says new and returning workers should build exposure to hot conditions gradually over seven to 14 days. Its schedule for new workers starts at no more than 20 percent of usual heat exposure on day one and adds no more than 20 percent on each later day.

A 2023 International Olympic Committee consensus says sports organizers should monitor conditions before and during an event, provide shade, cooling and hydration, and develop a clear heat policy with the relevant sports federation. It also places responsibility on athletes, organizers, medical teams and federations rather than treating heat safety as an individual's test of endurance.

Workplace schedules and sports rules are not interchangeable. Each setting needs its own authority, exposure assessment, rest arrangements and practiced emergency response.

A five-point plan turns advice into triggers

The plan can fit on one page, but it needs named responsibilities and decisions. Review it when an official warning changes or when a participant's health, medicine or activity level changes.

  1. Check the official local heat warning and forecast for the place and time of the activity.
  2. Identify children, older adults, pregnant people and people with chronic conditions or daily medicines who may need earlier action.
  3. Confirm shade, water, rest periods, a cool retreat and a way to contact local emergency services.
  4. Use the applicable employer or sports policy to shorten, move or cancel strenuous activity and to phase in heat exposure.
  5. After exposure, check for headache, nausea, dizziness or weakness and treat confusion, seizures, collapse or loss of consciousness as an emergency.

The person responsible for the plan should check conditions before departure and check everyone again after exposure. Any emergency sign should trigger immediate help and cooling, regardless of the forecast category.