When does salt work, and when does it not?

Bitter cold snap lessens salt's effectiveness

By Paul Gross - Meteorologist

DETROIT - Fun fact: salt isn't very effective against ice in bitterly cold temperatures.

Take a look at the chart above, you can see that at a temperature of 30 degrees, one pound of salt will melt 46 pounds of ice. As the temperature drops, salt's effectiveness slows to the point that when you get down near 10 degrees and below, salt hardly works at all.

Keep in mind that this is for nighttime temperatures; salt is effective at these very cold temperatures in sunshine. However, this can be dangerous when salt is applied to some snow and melts that snow, because then, if the overnight temperature drops below 15 degrees, that snow melt (which essentially becomes a saltwater solution) can refreeze into a layer of ice.

You may recall one time last winter when road crews didn’t salt for an entire week. We had to live with ice and packed snow on the freeways, because applying salt during the day would have just created more ice at night. Remember this whenever temperatures drop this low.

So what can you do if salt isn't going to work? Other ice melting products such as magnesium chloride (that's what I use at home) remain effective even with bitterly cold temperatures.

Not only does magnesium chloride work down to temperatures of -20 to -25 degrees, but it's also much more environmentally friendly. Salt is very caustic to your lawn, pets, and plants, whereas magnesium chloride is almost like fertilizer. The only drawback is that magnesium chloride costs about three times as much as salt, but I consider it a very wise investment.

And remember, always be careful in these bitter cold temperatures. This means a lot more than just bundling up. Pay extra attention to the pavement you are walking or driving on, so ice doesn’t sneak up on you and cause you big trouble.

Follow me on Twitter: @PaulGrossLocal4

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