How long will heat wave last and how high will temps go? – NBC Chicago

The first significant heat wave of the season is approaching the Chicago area this weekend, with sweltering temperatures and high humidity creating dangerous conditions for multiple days.

The worst of the upcoming heat wave is expected to reach the area during the daytime hours on Saturday, with hazardous conditions likely to persist through Monday evening.

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High humidity expected throughout the weekend will lead to overnight lows remaining in the mid-to-upper 70s, giving those without access to air conditioning no time to cool down before the next day's heat.

Has the forecast changed? Unfortunately, no. The heatwave starts tomorrow. Saturday through Monday still looks like the peak of the heatwave, though it may continue for some areas Tuesday and even into Wednesday. (1/5) pic.twitter.com/yXvMxaO5nL

The extreme heat and humidity will be exacerbated by strong winds ranging from 35-to-45 miles per hour throughout much of the region, creating a "blast furnace" effect.

The National Weather Service also warns that due to the stark difference in temperature from this week to this weekend's heat wave, those in the Chicago area have yet to acclimate to the blistering conditions.

Tomorrow will be the start of the heat wave with humidity making it feel over 100 degrees outside. It'll also be windy, leading to a "blast furnace" effect. We're not acclimated to this type of heat yet this year, so the difference from today to tomorrow will be stark. (2/5) pic.twitter.com/X7PGZQViOi

While suburbs far west and south of Chicago may see the worst of heat indices over the weekend, the entire region will see dangerous conditions for at least 72 hours.

Here's a view of the forecast through Monday. Each day will be similar with mostly sunny skies and oppressive heat. Don't forget the nighttime periods! It'll still feel like the lower 80s at midnight each night, which are the normal highs this time of year. (3/5). pic.twitter.com/ctuVgAupHH

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Overnight lows will be particularly dangerous in Chicago, where the urban heat island effect emits heat absorbed during the daytime hours at night, with buildings, concrete and asphalt serving as sources of heat.

The warm overnight temperatures limit the body's ability to recover for the next day's heat, making access to air conditioning crucial during the heat wave.

Overnight low temperatures through the heat wave will be stuck near 80 degrees in Chicago due to the Urban Heat Island effect. Such warm overnight temperatures in tandem with the long duration of the heat wave will be especially dangerous for vulnerable populations. (4/5) pic.twitter.com/U15ZyLw7T7

While the worst of the heat wave is expected to last through Monday evening, some parts of the region could see dangerous conditions persist into Wednesday, though there remains uncertainty in forecasts beyond the start of next week.