Community Corner

It's How Hot Outside?

What is the heat index? The National Weather Service offers an explanation. Plus, sort out the levels of warnings.

If you watch any newscast on the "dome of heat" engulfing the region, there’s one term that sticks out: heat index.

So, what’s a heat index?

The National Weather Service’s website explains heat index is “a measure of how hot it really feels when relative humidity is factored with the actual air temperature.”

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If the temperature is 100 degrees, the heat index may make it feel like it’s 120, according to NWS.

For example, Wednesday's temperature is expected to be 99 degrees but with relative humidity, it will feel like 105 to 115, experts said.

Find out what's happening in Huntleywith free, real-time updates from Patch.

The weather service decides to issue alerts if a heat index exceeds 105 to 110 degrees, the site states.

A list of possible alerts, described in the NWS’s site:

Excessive Heat Outlooks: issued when the potential exists for an excessive heat event in the next three to seven days. An Outlook provides information to those who need considerable lead time to prepare for the event, such as public utilities, emergency management and public health officials.

Excessive Heat Watches: issued when conditions are favorable for an excessive heat event in the next 12 to 48 hours. A Watch is used when the risk of a heat wave has increased, but its occurrence and timing is still uncertain. A Watch provides enough lead time so those who need to prepare can do so, such as cities who have excessive heat event mitigation plans.

Excessive Heat Warnings/Advisories: issued when an excessive heat event is expected in the next 36 hours. These products are issued when an excessive heat event is occurring, is imminent, or has a very high probability of occurring. The warning is used for conditions posing a threat to life or property. An advisory is for less serious conditions that cause significant discomfort or inconvenience and, if caution is not taken, could lead to a threat to life and/or property.

 


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