Enter the air temperature and the relative humidity to get the dew point and the associated humidity comfort level.
| Dew point range | Comfort level |
|---|---|
| Below 10°C (50°F) | Dry |
| 10°C to 13°C (50°F to 55°F) | Comfortable |
| 13°C to 16°C (55°F to 60°F) | Slightly humid, acceptable for most |
| 16°C to 18°C (60°F to 65°F) | Uncomfortable for many people |
| 18°C to 21°C (65°F to 70°F) | Very uncomfortable, muggy |
| Above 21°C (70°F) | Oppressive, typical of tropical climates |
These comfort levels are indicative and vary with individual acclimatisation and physical activity.
Why the dew point beats relative humidity as a comfort measure
Relative humidity is misleading on its own because it is relative to temperature: 90% relative humidity at 5°C carries very little actual moisture, while 50% relative humidity at 30°C carries a lot. The dew point, in contrast, is the temperature at which air becomes saturated with the water vapour it already holds and starts to condense as dew. Because it measures the actual amount of moisture in the air rather than a ratio, the dew point stays a reliable, absolute indicator of how muggy the air will feel regardless of the current air temperature. This calculator uses the Magnus-Tetens approximation, the formula commonly used by meteorologists including the UK Met Office to derive dew point from air temperature and relative humidity.
Comfort level by dew point
| Dew point range | Comfort level |
|---|---|
| Below 10°C (50°F) | Dry |
| 10°C to 13°C (50°F to 55°F) | Comfortable |
| 13°C to 16°C (55°F to 60°F) | Slightly humid, acceptable for most |
| 16°C to 18°C (60°F to 65°F) | Uncomfortable for many people |
| 18°C to 21°C (65°F to 70°F) | Very uncomfortable, muggy |
| Above 21°C (70°F) | Oppressive, typical of tropical climates |
What this calculator cannot do
The Magnus-Tetens formula is an approximation that is accurate for ordinary weather conditions but drifts slightly at extreme temperatures or very low humidity. It also does not account for wind or direct sunshine, which change how humid air actually feels on the skin. For the combined effect of heat and humidity on how hot the air feels, see the heat index calculator, which uses air temperature and relative humidity together to estimate heat-related illness risk.
Dew point and the UK climate
The UK's oceanic climate keeps dew points moderate for most of the year, with the Met Office reporting summer dew points that only occasionally climb past 18°C during the most humid spells, unlike the sticky, tropical-feeling conditions common in continental or coastal Mediterranean summers. When a dew point above 18°C does arrive in the UK, usually with a warm, humid air mass moving in from continental Europe, it is often remarked on precisely because it is unusual, and it tends to coincide with the muggy nights that make sleeping difficult even when the air temperature itself is not exceptionally high.