Weather Glossary: 35 Forecast Terms Explained in Plain Language

Weather apps use compact labels because a dashboard has limited space. This glossary expands the most common terms into plain-language explanations. It is designed as a quick reference rather than a technical meteorology textbook.

Temperature and moisture

Air temperature

The measured temperature of the surrounding air, normally reported in degrees Celsius or Fahrenheit. It does not directly describe how hot or cold your body will feel.

Feels-like temperature

An adjusted value intended to represent human thermal experience. Depending on the provider and conditions, it may account for humidity, wind and other factors.

Relative humidity

The ratio of actual water-vapor pressure to saturation vapor pressure at the same temperature, expressed as a percentage. It can change as the air warms or cools even when its moisture content changes little.

Dew point

The temperature to which air would need to cool for saturation to occur. Higher dew points generally indicate more moisture in the air and can feel more humid to people.

Heat index

A measure that combines heat and humidity to estimate how hot conditions may feel to the human body. It is mainly relevant in warm conditions.

Wind chill

An estimate of how cold exposed skin may feel when wind increases heat loss from the body. It applies to cold conditions, not warm weather.

Wind and pressure

Wind speed

The rate at which air moves horizontally. Weather services may use metres per second, kilometres per hour, miles per hour or knots.

Wind direction

The direction the wind is coming from. A north wind comes from the north and moves toward the south.

Wind gust

A brief increase above the sustained or average wind speed. Gusts matter for driving, outdoor objects, trees and exposed activities.

Atmospheric pressure

Force per unit area exerted by the atmosphere. Surface pressure applies at the location elevation; sea-level pressure is adjusted for comparisons across elevations. WeatherRadarNow displays surface pressure.

Pressure trend

The direction pressure is moving over time. A rising or falling trend can be more informative than one isolated pressure value.

Clouds and precipitation

Cloud cover

The approximate fraction of the sky covered by clouds, often displayed as a percentage.

Precipitation

Water falling from the atmosphere, including rain, snow, sleet or hail.

Probability of precipitation

The chance that measurable precipitation will occur at a specified location during a defined period. It does not directly tell you how long the rain will last or how heavy it will be.

Rainfall amount

The depth of liquid precipitation expected or measured over an area, commonly expressed in millimetres or inches.

Showers

Precipitation that is often intermittent and spatially variable. One neighborhood may receive a shower while another nearby remains dry.

Drizzle

Very small liquid water droplets falling from low cloud. It can reduce visibility even when accumulation is light.

Sleet

A term whose meaning varies by country. It can refer to a mixture of rain and snow or to ice pellets, so local weather-service definitions matter.

Hail

Balls or irregular pieces of ice that grow in storm clouds as supercooled water freezes onto them. Strong updrafts can keep growing stones aloft.

Visibility and atmospheric conditions

Visibility

The distance at which objects can be seen and identified. Fog, dust, smoke, precipitation and haze can all reduce it.

Fog

A cloud at or very near the ground that reduces visibility. Fog can vary sharply over short distances.

Mist

Small water droplets suspended near the surface, usually causing less severe visibility reduction than dense fog, though definitions vary.

Haze

A reduction in clarity caused by fine dry particles or aerosols rather than only water droplets.

Dust

Fine soil or mineral particles lifted by wind. Dust can reduce visibility and air quality.

Forecast and radar terms

Forecast

An estimate of future atmospheric conditions based on observations, numerical models and forecasting methods.

Nowcast

A very short-range forecast, often covering the next few hours and making heavy use of current radar and observations.

Model

A computer simulation that solves equations representing atmospheric processes to estimate future conditions.

Ensemble

A group of model simulations with slightly different starting conditions or configurations, used to explore forecast uncertainty.

Radar reflectivity

A measure of the energy returned to a weather radar by precipitation or other targets. Stronger returns often correspond to heavier precipitation, but interpretation is not always simple.

Radar echo

A signal returned to the radar. Not every echo is precipitation; birds, insects, terrain and propagation effects can sometimes appear.

Severe thunderstorm

A thunderstorm meeting defined severe criteria set by the responsible weather authority. Criteria differ between countries.

Watch

An official product indicating that hazardous weather is possible in or near an area. Exact terminology and meaning vary by national authority.

Warning

An official alert indicating hazardous weather is occurring, imminent or otherwise requires action. Always follow your local authority’s instructions.

Forecast confidence

A qualitative or quantitative indication of how certain forecasters are about an outcome. Confidence can differ for temperature, rain timing and storm location.

Forecast uncertainty

The range of plausible outcomes caused by incomplete observations, model limitations and the atmosphere’s sensitivity to small differences.