The fourth Extended Heat Warning of the summer is now in effect.

The Haliburton-Kawartha-Pine Ridge District Health Unit says hot and humid weather will be settling into the region this week.

The warning will be in effect until late Friday.

During the heat warning, residents are being reminded to keep cool, drink water and avoid outdoor activities.

The health unit says infants, elderly people, people with chronic diseases, and those who work outdoors are especially susceptible to heat-related illnesses.