Winter Weather Woes: How Effective is Salt in Freezing Conditions?
It’s a rite of winter in the Chicago area, alongside "dibs" and skating at Millennium Park, as residents pull out shovels and salt to deal with wintry weather.
Chicago’s Wintry Weather
The Chicago area hasn’t been hit with snow this winter, but this weekend’s brief warm-up and subsequent plunge back into frigid conditions have created some icy conditions around the region.
The Effectiveness of Salt in Freezing Conditions
These events have likely raised another key question in the minds of residents: how effective is salt when conditions get as cold as they have been? According to Cargill, an agricultural supply and food company, most types of rock salt do indeed have a "practical working temperature." While the Chicago area is typically above this temperature, this week’s weather has not been.
The "Practical Working Temperature" of Rock Salt
According to the company, the "practical working temperature" of rock salt is generally assumed to be around 15-to-20 degrees, with any readings below that causing diminishing rates of effectiveness. Data cited by the company shows that at 30 degrees Fahrenheit, a pound of salt can melt up to 46 pounds of ice, but at 20 degrees, that pound of salt can only melt around nine pounds of ice.
Salt’s Effectiveness at Lower Temperatures
When the temperature dips below 10 degrees, as the city of Chicago has had to deal with on Monday and will deal with again Tuesday, that effectiveness drops even more, according to officials with the company. In addition to being less effective overall, it also takes salt longer to melt ice at those temperatures, leading to slick spots on sidewalks and roadways.
Residents in the Far Southern Suburbs
For residents in Chicago’s far southern suburbs, especially in areas south of Interstate 80, the salt question will come back to the forefront overnight Monday and into Tuesday, as a system will move through, pushing a snowband over the area and causing limited accumulations. With low temperatures in the single-digits, slick spots could potentially occur on roadways, even those that have been treated with salt.
Temperatures to Warm Up
Fortunately, temperatures are expected to warm back up by Thursday and Friday, with readings soaring into the upper-30s and even the low-40s before plunging back into the teens or even single-digits by Sunday.
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Frequently Asked Questions
Q: How effective is salt in freezing conditions?
A: Salt is less effective in freezing conditions, with its effectiveness dropping as temperatures drop below 10 degrees.
Q: What is the "practical working temperature" of rock salt?
A: The "practical working temperature" of rock salt is generally assumed to be around 15-to-20 degrees, with any readings below that causing diminishing rates of effectiveness.
Q: How long does it take salt to melt ice at lower temperatures?
A: It takes salt longer to melt ice at lower temperatures, leading to slick spots on sidewalks and roadways.
Q: Will temperatures warm up soon?
A: Yes, temperatures are expected to warm back up by Thursday and Friday, with readings soaring into the upper-30s and even the low-40s.
