SIOUX CITY | Siouxlanders have likely seen their final positive thermometer readings of 2017.
As temperatures dipped below zero during the overnight hours Friday, they were expected to remain in the negative until Tuesday.
The result will be a brutally frigid New Year's weekend in Siouxland, with temperatures dropping dangerously low and wind chills bottoming out even lower -- to 30 to 40 below in some areas of the region.
The National Weather Service in Sioux Falls on Friday issued a Wind Chill Advisory extending through noon Saturday for the majority of Siouxland and a Wind Chill Warning for those farthest to the northeast: Osceola, Dickinson, Clay and Buena Vista.
Overnight wind chills will range from 15 below zero to 30 below zero for the advisory area and slightly colder temperatures ranging from 20 below zero to 35 below zero in the warning area.
NWS meteorologist Jim Murray said temperatures are expected to warm up just enough Saturday afternoon to escape an advisory, but as overnight temperatures continue to decrease throughout the weekend, more advisories and warnings will almost certainly be on the way.
The coldest night, he said, will be overnight Sunday.
"We're looking at a low of negative 23 on Sunday night in Sioux City," he said. "Wind chills are going to be down around 40 below. It's going to be really, really dangerous."
The weather service placed the Saturday morning overnight low at 6 degrees below zero, and the Saturday high is forecast for 4 degrees below zero. After that, the temperature is forecast to drop to 14 degrees below zero on Sunday morning, rise to only 7 degrees below zero in the daytime Sunday, and drop steeply to 24 degrees below zero by Monday morning.
The daytime Monday high is forecast for 3 degrees below zero. Then another big drop will occur overnight to 17 degrees below zero Tuesday morning, before warming follows, with the Sioux City high temperature to finally move above zero, at 17 degrees.
As Siouxlanders ring in 2018 on midnight New Year's Eve, the wind chill could be as low as 40 below zero in Sioux City and 42 below zero in Sheldon and Storm Lake, as well as in Beresford, South Dakota.
"We're not going to have a lot of wind through that period," Murray said. "It's just that the temperatures are so cold that even with a little bit of wind, it just drops it lower."
The coldest wind chills this weekend will be capable of causing frostbite in as little as 10 minutes to exposed skin, according to the NWS.
"Just protect yourself," Murray said. "Stay inside if you can. If you can't, dress warmly."
Siouxland saw a fresh blanket of snow Friday, and Murray said Sioux City could see an additional inch or so on Saturday evening.
The Woodbury County Sheriff's Office on Friday afternoon issued a news release encouraging caution for those traveling over the weekend, especially those driving in rural areas. The release recommended drivers allow plenty of time to reach their destinations, let someone else know where they are headed, keep their cellphones charged and have a winter weather emergency kit in their vehicles in case they become stranded.
The oncoming cold temperatures led the Iowa Department of Natural Resources Friday to cancel its annual First Day Hike Monday at state parks around the region, including Stone State Park. As of Friday afternoon, representatives at Ponca State Park in Nebraska said their 2 p.m. walk was still on.
The Journal's Bret Hayworth contributed to this report.