What is a common effect of increased relative humidity on air temperature?

Increased relative humidity affects air temperature by reducing the effective temperature variation experienced. When humidity levels are high, the air feels warmer to humans than it actually is because moisture in the air inhibits effective cooling through evaporation from the skin. This phenomenon can result in a smaller temperature spread, meaning the difference between the daily high and low temperatures is less pronounced.

Additionally, high humidity tends to stabilize the air, preventing significant temperature fluctuations that can occur in drier conditions. This stabilization occurs because the moisture in the air can limit the cooling that happens at night and can also slow the warming during the day, resulting in less overall variability in temperature. Thus, the common effect of increased relative humidity on air temperature is a decrease in temperature spread.