Humidity is the concentration of water vapor in the air. High levels of water vapor mean high humidity. Humidity can make the air feel wet or sticky and indicates the likelihood of precipitation, fog, or dew.
Humidity is important for animals who depend on sweating to regulate internal body temperatures. High humidity impairs heat exchange efficiency but reducing the rate of moisture evaporation from the skin. Therefore, when humidity is high, it can be hard to cool down because sweat can’t evaporate into the air like it needs to.
On a larger scale, humidity affects other aspects of life, such as local climate, animal and plant life, construction, vehicles, aviation, and global climate. Humidity affects the Earth’s energy budget, influencing temperatures in two ways. First, water vapor contains “latent” energy removed from surface liquid during transpiration or evaporation, cooling the Earth’s surface. Second, water vapor is the most present greenhouse gas and is a selective absorber. Water vapor absorbs the infrared energy radiated upward from the Earth’s surface, which is why humid areas do not cool down significantly at night, but desert areas do.
On weather reports, humidity is typically expressed as relative humidity, which is the amount of water vapor in the air expressed as a percentage of the maximum amount of water vapor the air can hold at the same temperature.
The dew point is the temperature then needs to be cooled to achieve 100% relative humidity. For example, a temperature of 40°F and a dew point of 40°F result in 100% humidity. A temperature of 80°F and a dew point of 60°F has a relative humidity of 50%.
What are the most humid cities in the world?
The most humid places in the world are located near the equator and the coast. Generally, the most humid cities are in South and Southeast Asia. The highest humidity ever recorded was a 95°F dew point in Saudi Arabia in 2003.
In the United States, the most humid states are Alaska, Florida, Louisiana, Mississippi, and Hawaii.
Sukkur, Pakistan, is located on the Indus River and is one of the most humid cities globally. Dew points can get as high as 86°F (30 °C) during monsoon season.
Cities such as Kuala Lumpur, Jakarta, and Singapore have very high humidities year-round because of their proximity to the equator and water. Kuala Lumpur, Malaysia, sees annual average humidity ranging from 74% to 86%. The average humidity in Jakarta can be up to 90%. The average relative humidity in Singapore is 84.2%, ranging from over 90% in the mornings to 60% in the afternoon.