Humidity vs. Latitude

Relative humidity (RH) is the ratio of the amount of water vapour (measured as grams of water per kilogram of air) in the air compared to the maximum possible at the given temperature. Cooling a parcel of air will decrease the amount of water vapour that is needed to reach saturation. Cold air has little capacity to hold water vapour, and this is one of the reasons the high latitude regions are effectively deserts with very low average annual precipitation. So although the polar regions are very dry, the air can still have a high relative humidity, and this is why there is no relationship between latitude (or temperature) and relative humidity.

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