Hottest temps in more than a decade expected in Ohio. What does heat advisory mean?

Sweltering heat is returning to Ohio and the Midwest on Tuesday and Wednesday.

Highs in the 96- to 98-degree range are in the forecast for Cincinnati , Dayton and Columbus. According to the National Weather Service, none of those cities have reached 98 degrees since 2012.

Some schools have announced early release due to the heat .

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The National Weather Service has issued heat advisories, and excessive heat watches and warnings for counties in Ohio. On Tuesday, most counties in the state, including those in the Greater Cincinnati region, were under a heat advisory, while some northern counties were under an excessive heat warning.

What is a heat advisory?

The weather agency's local offices issue heat alerts specific to the region. Criteria for the alerts vary for different regions. "For instance, residents of Florida are much more prepared for 90°F+ weather than residents in Alaska," the weather service states.

Here's what the alert levels generally mean, according to the National Weather Service :

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• Excessive Heat Warning − An Excessive Heat Warning is issued within 12 hours of the onset of extremely dangerous heat conditions. The general rule of thumb for this Warning is when the maximum heat index temperature is expected to be 105° or higher for at least 2 days and nighttime air temperatures will not drop below 75°. If you don't take precautions immediately when conditions are extreme, you may become seriously ill or even die.
• Excessive Heat Watches − Heat watches are issued when conditions are favorable for an excessive heat event in the next 24 to 72 hours. A Watch is used when the risk of a heat wave has increased but its occurrence and timing are still uncertain.
• Heat Advisory − A Heat Advisory is issued within 12 hours of the onset of extremely dangerous heat conditions. The general rule of thumb for this advisory is when the maximum heat index temperature is expected to be 100° or higher for at least 2 days, and nighttime air temperatures will not drop below 75°. Take precautions to avoid heat illness. If you don't take precautions, you may become seriously ill or even die.
• Excessive Heat Outlooks − The outlooks are issued when the potential exists for an excessive heat event in the next 3-7 days. An outlook provides information to those who need considerable lead time to prepare for the event.

Due to the increased risk for heat-related illness, the weather service is currently warning Greater Cincinnati residents to keep hydrated, stay in air-conditioned rooms, stay out of the sun and check on relatives and neighbors.

Anyone venturing outside should also take extra precautions, such as wearing lightweight or loose-fitting clothes and limiting strenuous activities to the early morning or evening.

Source: The National Weather Service in Wilmington, Ohio.

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This article originally appeared on Cincinnati Enquirer: Hottest temps in more than a decade expected in Ohio. What does heat advisory mean?