snow

[BANNIGAN]

Having a bit of a discussion at work (I know!!), but why does the temperature rise slightly before it snows?

[ronniemonda8]

'Latent Heat of Crystallization'. The process of making snow makes the snowflakes and makes them cold. They go cold.......they draw they add heat to the surroundings.

Something like that.

[mimififi]

I guess that is where the phrase "nah, it's too cold to snow" comes from.

Weird, I thought it was just some Bonkers old wives tale thing (which I normally quite like, being an old Wife but I always thought this was weird one) When will I learn, that the old wives of yesteryear, were obviously actual scientists!!!

[CT]

In general it might, but last year I was going home with my house mate. We'd been warned it was going to snow but at the time it was just raining and cold. Then a gust of cold air rushed past and temperature dropped noticeably. About 15 seconds after this the rain became snow.
Add the question to science as well.

[jake-the-peg]

You have to be carefull with the "old wives of yesteryear" they had a habit of getting things the wrong way around.

A good example is if swallows fly high it'll be good weather.

If swallows fly high they're chasing bugs that have been carried up high by existing high weather!

Willow bark for a headache and cloves for toothache is good though

Given that you get snow in the polar regions in conditions much colder than any old wife would have ever seen I think we can conclude that their Biochemistry was better than their meteorology!

[gen2]

There a few other factors that can give a temperature rise before snowfall.

1) Clear skies allow heat radiation to escape and the temperature will fall - that is why you get frosts on clear nights. When the sky is cloudy, it acts like an insulating blanket and the temperature will be higher. Snow falls from clouds, so as the weather changes from clear to cloudy, the temperature will rise.

2) Clouds form where warm moisture-laden air meets cold air which chills it to condense as rain or snow. The approach of the warmer air could be the temperature rise observed.

3) Temperature inversions: Under calm conditions, cold denser air sinks forming a layer of very cold air close to the earth's surface with warmer air above. As a weather front approaches, there will usually be an increase in wind speed. This will stir up the air and mix the cold dense air with the warmer air above and give a rise in temperature.