The National Weather Service has issued a heat advisory that will be in effect from 1 p.m. Tuesday until 8 p.m. Friday.

Heat index values – a measure of what the temperature feels like – are expected to be in the mid-90s on Tuesday and Wednesday afternoon, then near 100 degrees on Thursday and Friday afternoon. The highest index values will be inland from the Lake Erie and Lake Ontario shores.

Heat advisories begin when the heat index reaches 95 degrees.

The advisory includes Genesee, Livingston and Orleans counties in the GLOW region, and nearby counties of Niagara, Monroe, northern Erie and Ontario.

The advisory does not include Wyoming, southern Erie or Chautauqua counties, which are also expecting a prolonged period of heat and humidity this week, though initial temperatures will be a couple of degrees below those of the advisory area. It’s possible that a heat advisory could be issued later in the week as heat indices are expected to peak in the mid- to upper-90s Thursday and Friday afternoon.

For the current advisory area, high temperatures on Tuesday and Wednesday will likely be in the lower 90s on the lake plains away from the immediate lakeshores and in the valleys of the western Finger Lakes. Dewpoints will continue to slowly rise, and will reach the point of producing a higher heat index by Tuesday and Wednesday. Expect a heat index in the mid 90s both Tuesday and Wednesday in the lower elevation lake plain counties, and around 90 for the higher terrain, the Weather Service said.

Highs through the remainder of the work week will climb into the low to mid 90s in the lower elevations, while the higher elevations will see high temperatures in the upper 80s. Model guidance suggests a few mid to upper 90 degree readings in the typically warmer locations of our forecast area Thursday and Friday, the Weather Service said.

While the temperatures will soar, the humidity will also be on the increase. Dewpoint temperatures will continue to climb throughout the week, which will allow for the places in the lower terrain to see heat indices range from mid 90s to the possible 100, the Weather Service said.

Normal high temperatures for the region are around 80 degrees at this time of year, according to historical data from the Weather Service.

Warm overnight low temperatures will make it difficult to cool buildings without air conditioning.

The majority of the time will be dry, although a few widely scattered showers and thunderstorms are possible each afternoon and evening mainly well inland from the lakes, the Weather Service said in a forecast discussion.

A weak cold front will arrive Saturday and bring a better chance of a few showers and thunderstorms, and will also bring somewhat cooler temperatures to the region by Sunday, the discussion said.

The combination of hot temperatures and high humidity will combine to create a dangerous situation in which heat illnesses are likely. Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Young children and pets should never be left unattended in vehicles under any circumstances.

Anyone overcome by heat should be moved to a cool and shaded location.

Take extra precautions if you work or spend time outside. When possible reschedule strenuous activities to early morning or evening.

Wear lightweight and loose fitting clothing when possible. To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments.

Hot temperatures and high humidity may cause heat illnesses to occur. Know the signs and symptoms of heat exhaustion and heat stroke.

Muscle cramping is usually the first sign of heat-related illnesses (heat exhaustion or heat stroke).

Symptoms of heat exhaustion include nausea, vomiting, cold/pale/clammy skin, heavy sweating, fast and weak pulse, weakness or fainting and fast and shallow breathing. Victims of this illness should be moved to a cool place, be cooled using any method available such as ice packs; cool, wet cloths, or by applying water to the body, and sip on water. If a victim is continuously vomiting or loses consciousness, call 911 or your local emergency number immediately.

If heat exhaustion is not treated it may progress to heat stroke.

Symptoms of heat stroke include hot body temperature, hot/red/dry/moist skin, rapid and strong pulse and possible unconsciousness. Victims of this illness should be treated in the same ways as those with heat exhaustion but do not give fluids. Also, 911 should be immediately called, as heat stroke is a medical emergency.

Johnson Newspapers 7.1