High dew points contribute to mugginess and ‘tropical’ conditions

Summer is here and has brought its typical steamy feel as moisture in the air increases. There are several terms used by meteorologists to discuss atmospheric moisture and how it feels outside.

Humidity is a common word that can be measured in different ways, and most people are familiar with relative humidity, expressed as a percentage. Relative humidity is a gauge for how much of the air is saturated, which is useful for describing how intense moisture feels to our bodies. But, as the name says, this calculation is relative to the air conditions, and can be misleading.

Absolute humidity is a more uncommon measurement, which gauges the actual amount of water in the atmosphere as a weight. This value is independent of air temperature, but is not very useful to describe the effects or feel of humidity.

Another measure of moisture is derived from the humidity and temperature together. The well-known dew point is a hypothetical temperature where the atmosphere would be fully saturated at 100% humidity. The closer the air temperature is to the dew point, the more humid it will be.

The dew point is also relative to temperatures, but it can be useful to gauge how intense moisture feels. When dew points reach the 60s, humidity becomes noticeable, and the apparent temperature (another term for the heat index) can increase a few degrees above the air temperature.

If dew points reach 70 degrees or higher, the air can easily be described as muggy as moisture gets heavier. At that point, it feels sticky outside, and it is more difficult for sweat to evaporate and cool your body. Dew points in the upper 70s or 80s push into tropical territory, where humidity becomes oppressive and moisture may be visible in the air.

For this weekend, dew points will be at least in the upper 60s, and possibly mid-70s, teetering on the line of heavy mugginess to a tropical feel. Relief is finally expected from Tuesday to Thursday next week behind a cold front.