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Here’s the difference between heat alerts

File photo of the Jacksonville skyline. The city was under an Excessive Heat Warning Monday (File Photo).

JACKSONVILLE, Fla. – It’s been a hot summer, with numerous heat alerts issued.

Monday featured an Excessive Heat Warning for much of the area, with a Heat Advisory for areas to the north and south.

But what’s the difference between the heat alerts? And which one is worse?

Measuring the Heat Index

The heat alerts are not tied to air temperatures, but rather to the heat index.

According to the National Weather Service, the heat index is the apparent temperature that the body feels due to the combination of abnormally high air temperature and high relative humidity.

Meteorologists use a mathematical formula to create the heat index based on air temperature and humidity.

Clearly, in Northeast Florida and Southeast Georgia, heat indices can get quite high. But there are times they cross into dangerous territory.

Heat Advisory

When heat indices are forecast to get above 108° in the afternoon, a Heat Advisory is often issued.

Heat Advisories are an “advisory” that excessive heat conditions can be expected during the daytime hours.

A Heat Advisory is issued if the forecast heat index will climb above 108°.

Precautions need to be taken during the peak heating of the afternoon.

This includes drinking plenty of fluids, staying in air-conditioning if possible, limiting sun exposure, and checking in on relatives and neighbors, especially the elderly.

During heat advisories, the threat of heat illnesses increases. This includes heat exhaustion and heat stroke, which can be deadly.

Excessive Heat Watch

An Excessive Heat Watch is issued in anticipation of excessive heat conditions.

In this alert, hot conditions are not imminent, but rather it gives the public a “heads up” excessive heat conditions will be possible in the next 1-2 days.

An Excessive Heat Watch is issued 24-72 hours before an expected heat event.

Excessive Heat Watches are issued when the forecast heat index is expected to be near 115°.

These heat watches are converted into a Heat Advisory or an Excessive Heat Warning as we closer to the excessive heat event.

Excessive Heat Warning

An Excessive Heat Warning is issued when heat indices are forecast to be near 115° at some point during the day.

Excessive Heat Warnings are a category above a Heat Advisory and should be taken seriously.

An Excessive Heat Warning is issued if the forecast heat index will climb to near 115°.

Precautions need to be taken during the peak heating, including rescheduling outdoor activities.

The threat of heat-related illnesses increases dramatically during an Excessive Heat Warning.

If you must be outside, schedule regular breaks and drink plenty of fluids. You should also seek shade or air conditioning at the first sign of heat exhaustion.

We are used to the heat in Southeast Georgia and Northeast Florida. But the heat can become dangerous in this region, and heat alerts should be taken seriously.


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