A difference does not establish its cause

Air temperature of 28°C and apparent temperature of 25°C do not prove that cold air caused the difference. Apparent temperature is an estimate produced by a method; the difference alone cannot identify a specific cause. First check that both values refer to the same location and time.

Read wind and humidity separately

Wind and humidity can affect thermal experience, but not through one rule valid at every temperature. The US National Weather Service distinguishes cold-weather wind chill from hot-weather heat index. This does not mean every apparent temperature shown by WHENTHER uses those formulas. Do not substitute indicators with different definitions and valid ranges.

Separate current values from forecasts

Use current apparent temperature on local weather to understand the displayed current data. For an evening outing, also read the hourly forecast. The outing tool has no future apparent-temperature series, so it uses air temperature rather than adding today’s current difference to future hours.

Applying it to clothing

Shade, sunshine, indoor cooling, activity, garment thickness and personal differences cannot be settled by one number. Similar air and apparent temperatures do not mean comfort when both are below freezing. Read the absolute temperature and your activity times together. See the methodology for interpretation limits.

Sources and methods

WHENTHER · Content updated: 2026-09-21