Insider Blog: Higher dew points mean heavier moisture

Summertime mugginess has settled back into Mid-Missouri and will be a common part of the forecast the next few months. Most daily summer forecasts include humidity as a percentage but you may hear forecasters also mention dew points in the summertime. Dew points are a good measure of humidity across a range of temperatures and can also reflect how stable the atmosphere is.

The dew point is the "point" or temperature at which the air becomes fully saturated. When air temperatures and the dew point are close together this indicates higher humidity. Higher dewpoints also indicate more humidity as warmer air can hold more moisture.

Think of a warm summer day with highs right at 90 degrees (this is our seasonal average in Mid-MO in late summer.) When the dewpoint is at 60 on this given day (a 30-degree difference from the air) there will be little to no mugginess. But as dew points rise, say up to 70 degrees, at the same air temperature, the heat index will jump all the way to 96 degrees. As an easy rule of thumb in the summer, if the dewpoint is above the mid-60s to 70s, it will be uncomfortably humid.

Dew points can also give a measure of stability in the atmosphere. When more moisture is present in the atmosphere it can release more heat and instability to the surrounding environment. Lower dew points associated with less moisture would not be a good setup for convective storms. Typically dew points need to be higher than 55 degrees for strong storms to form. But this is just one of many ingredients that need to come together for storms to initiate.