When is it too late to put salt on your driveway?

Once the snow starts falling, is it too late to treat your driveway?

(NEXSTAR) — A sprawling winter storm is moving through the U.S., bringing snow to much of the Midwest on Tuesday. The same storm is expected to bring snow, rain and strong winds to the Northeast.

If you're in any of those communities (or another area that will undoubtedly see snow this winter), you'll likely be face to face with the ultimate decision: when should you put salt on your driveway or sidewalk, and is it too late to use it?

Ultimately, whether or not you should even use salt will depend on the precipitation and temperature you're experiencing.

Salt works by lowering the freezing temperature of the ice or snow it's added to, making it melt faster than if it remained untouched. However, once temperatures drop below 20 °F, ice melt becomes less effective, WSYR's Dave Longley explains. Below 15 °F, it's largely ineffective.

So if it isn't too cold, but snow or ice is in the forecast, when should you be putting down salt?

If you live in a cold weather climate, you already know salt is often applied before snow and ice move in. Longley recommends doing the same on your own pavement, as this can help prevent ice from forming. If you wait until the precipitation starts falling, you'll find your salt may have limited effectiveness.

"The best times are before the precipitation arrives and it is good to put some down after you finish shoveling or plowing," Longley explains. By putting salt down after you've cleared your driveway and walkways, you can get ahead of the likely wet surface turning to ice as temperatures drop after sunset.

How much salt you apply is largely up to you. If you use too much, you might find yourself with leftover salt residue or chunks on your driveway.

As Nexstar's WTEN reports, experts recommend using about a handful of rock salt per square yard. If you're using a calcium chloride ice melt, you can use less: about one handful for every three yards. That means in many cases, you may only need a coffee mug amount for your driveway, and possibly less for your sidewalk or other walkways.

While it may sound strange, you may even want to consider leaving some snow on the driveway or sidewalk. In many of the areas seeing winter weather this week, it has been relatively mild, meaning the ground is warm and hasn't frozen yet, Longley explains. This could lead to the accumulating snow melting from below, potentially creating a layer of ice. Leaving a bit of snow could give you a bit of traction rather than an icy surface.

If there is a layer of ice you're hoping to knock out without chipping away at it, Longley recommends a combination of salt and sunshine, if you're lucky enough to get some. If it doesn't completely melt the ice, it should at least make it easier to remove.

Rock salt and calcium chloride, both commonly used to tackle ice, have been known to damage pavement, cause rusting on cars, and even pollute water. If you're looking for a less-harmful means of melting ice (and the sun isn't helping you), the Denver's Department of Environmental Health recommends magnesium chloride, which is also considered the most pet-safe option by the ASPCA; calcium magnesium acetate; or a "carbonate-based solution."

The Associated Press contributed to this report.