Sweltering heat is expected across Ohio and the Midwest this week.
According to the National Weather Service in Wilmington, the heat index could reach 105° in Greater Cincinnati, with dewpoints in the 70s and temperatures in the mid-90s to low 100s over the next few days.
Much of the region is under a heat advisory from noon Monday, June 29, through 8 p.m. Thursday, July 2, as officials warn that high heat and humidity increase the risk of heat-related illness.
Local weather service offices issue heat alerts when hazardous conditions are expected, but the criteria vary by region.
Here’s what the alert levels generally mean, according to the National Weather Service:
What is a heat advisory?
A heat advisory is typically issued when the heat index is between 100° and 104°. Heat advisories are also issued for dangerous heat conditions that are not expected to reach warning criteria.
The NWS advises that people limit their time outside by postponing or rescheduling outdoor activities. If you must be outside, be sure to stay hydrated and take frequent breaks in the shade or in cool spaces.
What is an extreme heat watch?
Extreme heat watches and warnings are issued when the heat index is 105° or greater. Extreme heat watches, however, are issued when forecasters see the potential for extreme heat, but details on timing and severity remain uncertain.
The NWS advises that individuals should plan to suspend all major outdoor activities and make arrangements for a cool place to stay if they don’t have air conditioning.
What is an extreme heat warning?
An extreme heat warning is issued when extremely dangerous heat conditions are expected or happening.
Avoid outdoor activities during the hottest part of the day, stay in air-conditioning as much as possible − even overnight − and check on family, friends, and neighbors.
What is the heat index?
The Heat Index shows how hot it feels when humidity and air temperature are combined, according to the National Weather Service.
It reflects how comfortable it is outdoors, since the body feels hotter in humid conditions. In humid conditions, sweat evaporates more slowly because the air already holds more moisture, reducing the body’s ability to cool itself.
What’s the difference between temperature and heat index?
The temperature is the actual air reading − what a thermometer records in the shade. The heat index represents how hot it feels when temperature and humidity are combined, according to the National Weather Service.
High humidity slows sweat evaporation, making it harder for the body to cool down.That’s why the heat index is often higher than the air temperature, and why it’s used to gauge the risk of heat-related illness.
How hot will temperatures get in Cincinnati?
For Cincinnati, the coolest day of the stretch will be Monday, June 29, with highs in the low 90s. The heat index will be about 103. The hottest day will occur on Thursday, July 2 when temperatures are expected to hit 97 degrees, before gradually falling back to a high of 93 by Sunday, July 6.
What is a heat dome?
According to AccuWeather, a heat dome forms when a large, stagnant ridge of high pressure traps hot air near the ground, creating prolonged periods of intense heat, high humidity, and little relief.
Contributing: David Ferrara and Cheryl Vari, The Cincinnati Enquirer; Brandi D. Addison, USA TODAY Network.
This article originally appeared on Cincinnati Enquirer: What is a heat advisory? Ohio heat wave brings 100-degree temps
Reporting by Haadiza Ogwude, Cincinnati Enquirer / Cincinnati Enquirer
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By Haadiza Ogwude, Cincinnati Enquirer | USA TODAY Network
