Need Help?
(423) 496-5141
City Hall Hours
Mon - Fri 8:00 am - 4:00 pm
Here's what you need to know: The rock salt and salt brine that road crews spread on your local roads both stop working when it gets too cold. Understanding this 15°F temperature limit is important for staying safe on winter roads.
-40°F
-20°F
0°F
20°F
32°F
🧂 Rock Salt (Solid)
Stops Working at 15°F
What is it? This is the white/gray salt crystals you see trucks spreading on roads in winter.
How it works: The salt needs to dissolve in moisture on the road to create a liquid that prevents ice from forming.
The Problem: Works great when it's around 20°F or warmer, but once it drops to 15°F or below, it pretty much stops melting ice. The salt just sits there as useless crystals.
Best used: Before a storm when temperatures will stay above 20°F, or after plowing to prevent refreezing.
💧 Salt Brine (Liquid)
Stops Working at 15°F
What is it? A liquid mixture of salt and water (about 23% salt) that trucks spray on roads.
How it works: The liquid spreads more evenly than crystals and sticks to the road better. It's already dissolved so it starts working faster.
The Problem: Has the same temperature limit as rock salt - stops working at 15°F. Below this temperature, it freezes into a useless slush.
Best used: Applied 24-48 hours before a storm as a preventative coating, but only when temps stay above 15°F.
What This Means for Your Safety
- When it's 15°F or colder, both rock salt and brine stop working – they just sit on top of the ice doing nothing
- Brine sprayed before a storm only helps if the temperature stays above 15°F during the entire storm
- Don't assume roads are safe just because you see salt on them – in extreme cold, treated roads can still be just as icy
- In really cold weather, snowplows and sand are the only things that help – salt-based products just won't melt the ice
- Black ice is extra dangerous when it's below 15°F because salt can't prevent or melt it
Driving on Untreated Snow = Instant Ice
Here's what happens when salt isn't working:
When you drive on snow-covered roads in temperatures below 15°F, your tires compress and compact the snow. The pressure from your vehicle, combined with the friction, creates enough heat to melt the bottom layer of snow just slightly.
The dangerous part: Because it's so cold and the salt can't work, this thin layer of melted snow immediately refreezes into a smooth, slick layer of ice. Each car that drives over it packs it down more, making it harder and slicker.
The result: What started as somewhat manageable snow becomes a dangerous ice rink. This is especially bad on hills, curves, and intersections where cars brake and accelerate. Without salt working, there's nothing to prevent this cycle.
This is why roads can actually become MORE dangerous after traffic drives on them in extreme cold!
