Heat advisory issued for Suffolk Wednesday as heat index nears 100

A heat advisory is in effect for northeast and southeast Suffolk counties from 11 a.m. to 9 p.m. Wednesday, according to the National Weather Service in Upton.

Heat index values — what it feels like when humidity is factored in — are expected to reach up to 100 degrees. The weather service said hot temperatures and high humidity may cause heat illnesses.

Forecasters said an expanding ridge of high pressure aloft will bring a capped, mostly sunny air mass, with the highest temperatures expected Wednesday. Highs are forecast to reach the low to mid-90s locally, with dew points well into the 60s pushing heat index values toward 100. The weather service also noted that a more westerly wind Wednesday will help limit the cooling marine influence along the immediate coast, allowing the heat to spread farther east.

In Riverhead, the National Weather Service forecast calls for sunny skies Wednesday with a high near 93 and heat index values as high as 99. A slight chance of showers is possible between 2 to 5 p.m., followed by a slight chance of showers and thunderstorms later in the afternoon and evening. The chance of precipitation is 20%.

The weather service said seniors and people with chronic health problems or mental health conditions are at increased risk, and homes without air conditioning can be much hotter than outdoor temperatures.

Officials recommend using air conditioning to stay cool at home or going to an air-conditioned location. Those without home air conditioning should continue seeking cool spaces each day as long as it remains hot, and for a few days after if the home remains hot. Residents are also urged to check on vulnerable friends, family members and neighbors.

For outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air-conditioned environments. Anyone overcome by heat should be moved to a cool, shaded location. Heat stroke is an emergency; call 911.