Weather Forecast Guide

This guide provides information on the icons used in the forecasts, as well as explaining some of the mode in-depth features.

Layout

Choose from different forecast layouts: view hour by hour forecasts in Classic or Timeline, or 16 day forecasts in Classic, Table, or Timeline.

The Timeline view is especially useful for tracking expected changes in weather throughout the day.

Timeline forecast


Rain and precipitation

Forecast rain totals for the given time period are shown in mm.

The chance of rain is given on some forecasts as a percentage. It is calculated by analyzing the forecasts over a grid surrounding your location. The area of the grid is dynamically changed to increase confidence, based on the model being used and the time of year.

For example, if the chance of rain is 50%, it means that rain is forecast for 50% of the grid points surrounding your location.

The thunderstorm risk is based on the Convective Available Potential Energy (CAPE) forecast for your selected location.

Snow forecasts are based on the precipitation type variable provided by computer models. In some cases, additional processing is done that factors in dew points and temperatures.

Wind

Wind direction, mean wind speed and gust wind speed forecasts are provided.

Wind direction is in degrees. By default, mean wind speed and gust wind speed are displayed in mph, but km/h and kts are available from the unit selector.

Temperature

Temperature forecasts by default are displayed in Celcius, but Fahreinheit can be chosen from the units selector.

Typically, nighttime values use the minimum temperature variable (where available) from the computer model, while daytime values use the maximum temperature variable (where available).

A value for "feels like" (sometimes called wind chill) is displayed on some of the forecasts. This refers to how cold the air feels on your skin due to the combination of air temperature and wind speed.

UV index

The UV index is a measure of the strength of the sun's ultraviolet (UV) radiation at a particular place and time.

The UV index scale typically ranges from 0 (low) to 11+ (extreme). The higher the number, the stronger the UV radiation, and the greater the risk of sunburn and skin damage.

It is important to take precautions to protect yourself from the sun when the UV index is 3 or higher.

The maximum expected UV index for the day is displayed on the 16 day forecasts for the first 4 or 5 days of the period.


Icons

The icons show the predominant weather type at the given forecast time.

18°C
Temp
Wind direction

Wind direction

Sunny Clear

Sun / Clear

Fair, sun and clouds Fair, clear and clouds

Sun / Clear periods

Mostly cloudy Mostly cloudy

Sun / Clear intervals

Cloudy Cloudy

Cloudy

Light rain Light rain

Light rain

Heavy rain Heavy rain

Heavy rain

Showers Showers

Showers

Thunderstorm and possible hail Thunderstorm and possible hail

Thunder

Sleet Sleet

Sleet

Snow showers Snow showers

Snow showers

Light snow Light snow

Light snow

Heavy snow Heavy snow

Heavy snow


Guidance

This is designed to add context to the weather forecast. For example, if rain rates are forecast to exceed a defined level, a notification warning about the possibility of dangerous driving conditions is given.

Will it, MOGREPS-G and GEFS forecasts

These provide data from ensemble models, which show the likelihood of different outcomes.

Probability forecasts offer a more realistic picture of the weather outlook beyond a few days by expressing the likelihood of different outcomes. Instead of a single deterministic forecast (e.g., "sunny"), you might see probabilities for different conditions (e.g., "60% chance of rain, 40% chance of clouds").



COMPUTER MODELS

INFO

Short range
Short to medium range
Medium to long range
Deterministic
Ensemble

See the Model inventory for the full list of model charts and data