Admittedly, I delayed the hour of my walk today in favor of a higher temperature. But even at 11am, even as the sun’s rays reflected brilliantly off the snow, the thermometer read “11.” And a local observation station said it went down to 6 degrees last night.
Six? That’s under the threshold in which salt (sodium chloride) no longer melts ice.
Here in Pennsylvania, road crews (under pressure from the public) use a frivolous amount road salt. Much suffers as a result (cars, fish, plants, streams, road surfaces) but that’s a topic for a much longer essay.
Instead, today’s post is about science. The concentration will make a difference, but it’s safe to say that salt won’t liquify ice when the air temperature is under seven degrees. Road crews tend to use 15 as a threshold.
So be careful out there. Standing moisture, unless treated with something other than salt, could be frozen into “slipperyness.” It’s all a matter of degrees.