What Is an Extreme Cold Warning and What Does It Mean? Guidance Checked November 5, 2026

Verified: November 5, 2026, at 21:09 UTC (UTC+00:00).

An extreme cold warning means dangerously low temperatures or wind chill are expected or occurring in an affected area. In the United States, the National Weather Service uses the warning when cold conditions are severe enough to threaten health or life. The temperature that triggers it depends on the local forecast office, so the warning text matters more than a single universal number.

For readers in Australia, the phrase may appear in overseas news or travel alerts. Australia’s Bureau of Meteorology provides its own local forecasts and warnings, including frost and sheep graziers’ warnings. Check the agency responsible for the place you are in or visiting; this explainer does not establish that a particular warning is currently active.

Destaques

• A warning signals dangerous cold that is expected or already occurring; a watch signals that dangerous conditions are possible.
• Thresholds vary by location, and dangerous cold can occur even without strong wind.
• Wind chill describes how the combination of wind and cold affects exposed skin; it is not the measured air temperature.
• In Australia, use Bureau of Meteorology forecasts and warnings for your location, and treat suspected hypothermia as an emergency.

What does an extreme cold warning mean for you?

It is a prompt to check the affected area, timing and expected conditions, then reduce exposure to the cold. A warning is not necessarily a forecast of snow or a blizzard. Very low temperatures alone can be dangerous, including on a clear, calm day.

In the United States, an extreme cold warning can cover dangerously cold air temperatures or wind chill. The National Weather Service’s Spokane office, for example, describes a warning as conditions that are expected or occurring, while a watch means they are possible. The exact wording and timing in the alert tell you whether your location is included and when the risk is expected to be greatest. See the National Weather Service’s alert definitions.

In Canada, the federal weather service says cold warnings are based on expected impacts from temperature and wind chill, with criteria that differ across the country. Its alerts describe the expected period, health impacts and protective steps. The terminology and thresholds used by one country should not be assumed to apply in another. Read Canada’s cold warning guidance.

What temperature triggers an extreme cold warning?

There is no single worldwide threshold. Weather services account for local climate and the impacts a given temperature can have. For example, the National Weather Service office in Indianapolis lists a warning threshold of an air temperature or wind chill of −20°F (about −29°C) or colder. Its Wilmington office uses 5°F (about −15°C) or colder for its warning area. These are local examples, not rules for all of the United States or for Australia. See the Indianapolis criteria and Wilmington criteria.

Read the actual alert for the forecast temperature, wind chill, duration and affected districts. Conditions may vary within a warning area, particularly across elevations or exposed terrain. A forecast can also change, so check for updates before traveling or spending time outdoors.

How does wind chill make cold weather more dangerous?

Wind removes the warmer layer of air close to exposed skin, increasing the rate at which the body loses heat. Wind chill expresses that combined effect as an equivalent temperature. It helps communicate the risk to people outdoors, but it does not mean the thermometer has dropped to the wind chill value.

Wind is only one part of the risk. Wet clothing, long exposure and inadequate shelter can make it harder to retain heat. Cold injury can occur even without an official warning, including in temperatures near freezing. Canada’s weather service explains that extreme cold can be hazardous with little or no wind.

What cold weather warnings should Australians check?

Start with the Bureau of Meteorology’s warnings and alerts and the forecast for your specific location. Its frost warnings focus on conditions that can damage frost-sensitive plants; its sheep graziers’ warnings address conditions that can threaten vulnerable livestock. Neither should be treated as a direct equivalent of a US extreme cold warning for human exposure.

The Bureau says frost warnings are available in Tasmania, Victoria and South Australia. Its forecasts can also mention frost elsewhere. Frost and cold exposure are related but different hazards: a frost forecast can help identify potential icy conditions or crop damage, while a person’s risk also depends on wind, wetness, shelter and exposure time. See the Bureau’s guide to frost forecasts.

Who is most at risk, and what happens next?

Anyone exposed to severe cold can be harmed, but infants, older adults, people without adequate shelter, outdoor workers and people with some medical conditions may face greater risk. Frostbite damages skin and underlying tissue; hypothermia occurs when the body loses too much heat. Warning signs of hypothermia can include shivering, clumsiness, confusion and slurred speech.

If hypothermia is suspected in Australia, call triple zero (000) for an ambulance. Move the person somewhere warm and dry if it is safe, remove wet clothing and cover them with blankets while waiting for help. Follow the emergency operator’s instructions. Healthdirect’s hypothermia guidance has further first-aid advice.

A warning may be updated, extended or allowed to expire as forecasts change. Its expiration does not automatically mean every place is safe: check the latest forecast and conditions, especially before an early start, a mountain trip or a long journey.

FAQ

Is an extreme cold watch the same as a warning?

No. In US National Weather Service terminology, a watch means dangerous cold is possible; a warning means it is expected or occurring. Check the issuing agency’s wording wherever you are.

Can you get hypothermia without snow or a warning?

Yes. Hypothermia can develop in many environments, including when a person is wet and exposed to cold for a prolonged period.

Does an extreme cold warning mean schools will close?

Not automatically. Closures are decisions for local authorities and individual schools. Check their official announcements for your area.