The National Weather Service has issued a heat advisory until 7 tonight that includes Livingston, Monroe and Ontario counties.

High temperatures are forecast to reach the mid 80s and even approach 90 degrees in some locations. When combined with the high humidity could create heat index values in the mid 90s.

The heat index is a measure of what the temperature feels like.

The conditions may cause heat illnesses to occur.

There is a marginal risk for strong to severe thunderstorms this afternoon and evening. This risk includes the potential for damaging wind gusts, small hail and heavy rainfall.

The Weather Service is advising people take it easy if possible — 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.

The Geneseo Police Department has responded to several such complaints in recent weeks, and noted the increased health risk as temperatures have warned. Temperatures inside vehicles can quickly surpass 100 degrees. on a 90-degree day, the interior temperature can reach as high as 160 degrees in less than 10 minutes.

During a recent complaint of an animal left in a vehicle that Geneseo Police responded to, the temperature inside the vehicle was recorded at 120 degrees and the animal was in distress, according to Police Chief Eric Osganian.

Take extra precautions if you work or spend time outside. To reduce risk during outdoor work, the Occupational Safety and Health Administration recommends scheduling frequent rest breaks in shaded or air conditioned environments.

Other heat safety advice:

■ Wear lightweight and loose fitting clothing when possible.

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

■ Heat stroke is an emergency. Call 911 if it occurs.

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.

Here is a forecast from the National Weather Service for the Genesee Valley:

This Afternoon

A slight chance of showers, then showers and thunderstorms likely after 1pm. Partly sunny and hot, with a high near 90. Southwest wind 3 to 5 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight

Showers and thunderstorms likely, mainly before 2am. Mostly cloudy, with a low around 68. Light and variable wind becoming south around 5 mph after midnight. Chance of precipitation is 60%. New rainfall amounts between a quarter and half of an inch possible.

Tuesday

Showers and thunderstorms, mainly after 2pm. Some of the storms could produce small hail, gusty winds, and heavy rain. High near 87. Southwest wind 7 to 10 mph, with gusts as high as 20 mph. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tuesday Night

Showers and thunderstorms before 9pm, then a chance of showers. Low around 63. South wind 8 to 10 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Wednesday

A slight chance of showers. Mostly sunny, with a high near 78. West wind 10 to 13 mph. Chance of precipitation is 20%.

Wednesday Night

A slight chance of showers before 9pm. Partly cloudy, with a low around 56. Chance of precipitation is 20%.

Thursday

A chance of showers after 3pm. Mostly sunny, with a high near 77. Chance of precipitation is 40%.

Thursday Night

A chance of showers before 9pm. Partly cloudy, with a low around 58. Chance of precipitation is 40%.

Friday

Mostly sunny, with a high near 80.

Friday Night

A chance of showers after 3am. Partly cloudy, with a low around 61. Chance of precipitation is 30%.

Saturday

Showers likely and possibly a thunderstorm. Mostly cloudy, with a high near 81. Chance of precipitation is 60%.

Saturday Night

Showers likely and possibly a thunderstorm. Mostly cloudy, with a low around 64. Chance of precipitation is 60%.

Sunday

A chance of showers. Partly sunny, with a high near 82. Chance of precipitation is 40%.

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