SARANAC LAKE — It’s looking like a sweltering start to next week as temperatures throughout the Tri-Lakes are forecasted to soar to roughly 20 degrees Fahrenheit above normal, according to the National Weather Service’s Burlington, Vermont office, which serves northeastern New York.

Monday is expected to be the hottest day of the stretch, followed closely by Tuesday, with high temperatures expected in the mid and low 90s, respectively, according to NWS Burlington Meteorologist Eric Myskowski. Additionally, he said high levels of humidity will make things feel even warmer, with the heat index — a measure of what the temperature feels like to the human body when relative humidity is combined with the air temperature — values expected to run a few degrees above the actual highs.

Meteorologists often rely on this when issuing heat-related alerts or forecast guidance, as it’s a more reliable indicator of how people’s bodies will react to the heat than the air temperature itself. The reason? Sweat. Humans perspire as a way to cool down when our bodies become overheated. The cooling comes as sweat evaporates, causing an endothermic reaction as it draws heat away from the body in order to turn from a liquid into a gas.

During humid conditions, when there is more moisture content in the surrounding air, sweat does not evaporate as readily, making it more difficult for the body to cool itself off. This can increase the potential for heat stroke and heat-related injuries. Meteorologists are urging people to play it safe, especially given that heat events of this magnitude are not common in the Tri-Lakes area. This includes checking in on family members and neighbors, especially if they are elderly or have health conditions that increase their risk.

“Try to avoid strenuous activity outside,” Myskowski said. “If you do have to … do it in the evening or the morning before the heat of the day. Stay hydrated and, if you can, try to find a place with air conditioning or cooling.”

A cold front is expected to sweep across the area later Tuesday, returning temperatures to more seasonable values for the second half of the week.

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The setup

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Myskowski said the unusually intense heat — even for this time of year — is being driven by the presence of a strong area of high pressure that will set up over the mid-Atlantic region. High-pressure systems have a clockwise rotation around them. Therefore, it will push a hot and humid air mass originating in the Caribbean and southern U.S. to the north as it remains in place for an extended period of time.

Besides the air mass, high pressure generally results in fair weather, and the lack of cloud cover or rain will allow for robust diurnal heating from the sun’s radiation. That’s because high pressure tends to inhibit warm air rising from near the surface up into the atmosphere, the precursor for precipitation events, especially summer thunderstorms. This results in a ‘heat dome,’ essentially trapping the hot air over an area until the high-pressure system gets displaced.

While heat of this magnitude is rare for this area, heat domes are a common weather phenomenon during the warm season. Myskowski said that the numbers fluctuate each year, but it’s typical for northern New York to get a heat dome like this once or twice per season.

If the current forecast holds, records could fall. According to NWS Burlington data, Monday’s current record high temperature for Saranac Lake stands at 89 degrees Fahrenheit, set in 1964. Tuesday’s record is 90 degrees Fahrenheit, set in 2003.