Why the heat index won’t be as great tomorrow despite there being higher temperatures

KANSAS CITY, Mo. (KCTV) - As we continue with dangerous heat across the Missouri River Valley, a fascinating, warm air phenomenon will develop through the next few days.

This afternoon temperatures are expected to soar into the middle and upper 90s and with the humidity above 70%, the heat index will rise to a stifling range between 110° and 115°.

Moreso, the high temperature for Wednesday afternoon and Thursday is expected to flirt near 100°. Now you would think the heat index would be even hotter but instead the heat index is expected to range between 105° and 110°.

So why do we see a decrease in the heat index even though we are increasing the air temperature?

The answer lies with the humidity. As we move into Wednesday afternoon, some of the moisture that has been trapped at the surface will have an opportunity to escape either to the middle and/or upper levels or be forced into what’s left of Tropical Storm Herald as it continues its trek across southern Texas into the desert southwest.

FORECAST: Weather Alert Tuesday as we remain under life-threatening heat with poorer air quality

Our humidity is more likely to range between 50% and 70% on Wednesday which would yield a completely different heat index. We anticipate the same scenario for Thursday, which is the final day of our excessive heat warning. The air temperature is expected to be at its hottest since the heat wave began.

Air temperatures are more confident in the triple digits that day than any other day under the excessive heat warning. This is due to the heat dome beginning to move back to the southwest. Much like a candle burns brightest just before it goes out, the heat dome will produce air temperatures at its hottest before it exits.

However, due to the humidity also, leaving the area, feel-like temperatures are expected between 105° and 110°. Now we will continue to monitor this upper-level ridge, or heat dome, closely. And, depending on its movement along with tropical weather entering Texas, we may alter the heat index values.

If this happens, we will be the first ones to warn you.

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