GLASGOW, Ky. — An Extreme Heat Warning is now in effect for Barren County and much of Kentucky through Thursday evening, with forecasters warning that heat index values could reach as high as 115 degrees.

The National Weather Service upgraded its previous Heat Advisory to an Extreme Heat Warning on Monday, citing dangerously hot conditions and little overnight relief from the heat and humidity.

Forecasters expect heat index values, what the temperature feels like when humidity is factored in, to range between 100 and 115 degrees during the warning, which remains in effect until 8 p.m. CDT Thursday.

The combination of high temperatures and humidity significantly increases the risk of heat-related illnesses, particularly for older adults, young children, people with chronic health conditions and those who work or spend extended periods outdoors.

Unlike many summer heat events, overnight temperatures are expected to remain warm and humid, providing little opportunity for the body to recover before daytime temperatures climb again.

The National Weather Service urges residents to drink plenty of water, spend time in air-conditioned buildings when possible and avoid strenuous outdoor activity during the hottest parts of the day.

Anyone who must work outside should take frequent breaks in the shade or an air-conditioned space and wear lightweight, loose-fitting clothing.

Officials also remind residents to check on elderly neighbors, family members and others who may be vulnerable to the heat.

Children and pets should never be left unattended inside vehicles, where temperatures can become deadly within minutes.

The warning covers Barren, Allen, Butler, Cumberland, Edmonson, Hart, Logan, Metcalfe, Monroe, Simpson and Warren counties, along with much of central Kentucky and southern Indiana.