SIOUX FALLS, S.D. (KELO) — The National Weather Service has placed a portion of southeastern South Dakota under an excessive heat warning, with heat index values expected to reach as high as 115°F.

KELOLAND Meteorologist Brian Karstens took a deep dive into the forecast in the coming days, including what the heat index should look like for the next few days.

The NWS issues excessive heat warnings when heat index values are expected to reach or surpass 110°F and not fall below 75°F for at least a 24-hour period, meaning there will likely not be much in the way of a break in the heat in the immediate future.

The heat index, according to the NWS, is a measure of how hot it feels outside. The dew point has been high lately, which combined with the temperature itself, makes for a high level of humidity.

Thanks to a dew point of 77° today, the humidity in Sioux Falls is at 70%. That, combined with the 88°F air temperature, makes for a heat index of 100°F.

Heightened heat indexes can be dangerous, as they can lead to overheating by those out in the elements. KELOLAND News spoke recently to Sanford sports scientist Thayne Munce, who explained that increased humidity makes it more difficult for the body to cool itself.

The human body produces sweat, which is meant to evaporate off our skin, carrying away body heat as it does so. The higher the humidity, Munce explained, the harder it is for that sweat to evaporate and cool you.

This struggle to cool the body can lead to rising bodily temperature and increased fluid loss, putting you at risk.

The heat itself isn’t the only factor at play in terms of risk either, as the UV index — the expected risk of overexposure to UV radiation from the sun — is also elevated.

The UV index as of 2:00 p.m. on Monday is at an 8 — very high — meaning safe time in the sun without protection is as low as 15-30 minutes.

To minimize risk, time out in the heat should be limited, and water should be consumed throughout the day.