Calculate the dew point temperature. According to Wikipedia, dew point is the temperature to which air must be cooled to become saturated with water vapor, assuming constant air pressure and water content. When cooled below the dew point, moisture capacity is reduced and airborne water vapor will condense to form liquid water known as dew. When this occurs via contact with a colder surface, dew will form on that surface. The dew point is affected by humidity. When there is more moisture in the air, the dew point is higher.
Using the table below, the "comfortable zone" can be calculated. The "uncomfortable" zone (dew point above 18 deg Celcius) is the zone where people will feel uncomfortable and sticky because a higher humidity room will make sweat less likely to evaporate.
Dew point and humidity also explain why people tend not to sweat in deserts because desert climates have low humidity despite high temperatures, whereas tropical rainforests have lower temperatures but feel more sticky.
