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It's a saying we hear regularly, but can it ever be too cold to snow?
Well....not really! - seems to be the answer. At least, not within the environmental conditions that most of us are used to, especially here in the UK. Conversely, it doesn't have to be a literally freezing 0°C for us to get snow and in the UK the heaviest snow falls tend to occur when the air temperature is somewhere between 0 °C and 2°C, according to the Met Office.
Generally speaking, for snow we need:
- A temperature profile that will allow for snow to reach the ground without melting too quickly
- Air which can hold enough water vapor (which has the potential to become snow)
- Some mechanism to allow the lifting of that 'saturated' air which allows snow to form at higher, cooler temperatures before descending to the ground when it becomes too heavy to be suspended
Anyway, back to the phrase...
- We frequently see conditions where it is too warm to snow, as ice crystals cannot form and / or make it to the ground, but...
- ...We almost never see conditions where it is physically too cold to snow, though the size of the flakes and whether it appears at ground level as typical 'snow' or ice crystals for example, can be affected. Snow can occur at extremely low temperatures providing there is a source of moisture and some way to lift or cool the air
- Still, very cold air, say around -20°C, holds less water vapour, which in turn reduces the amount of ice crystals that can be formed, which in turn makes typical 'snow' less likely, but far from impossible. If the temperature were to fall to around -40°C however, then the amount of water vapour the air could hold would be low enough to make snowing unlikely and any snow that did fall would be minimal
- In conclusion, as a casual phrase 'Too cold to snow' is really a bit of a flaky old saying, as we rarely see temperatures where the relationship between very cold and very dry air comes into play in this way
So next time you hear someone say 'Oh no, it's too cold to snow', you might think 'Is it, though?' Don't think it too loudly of course, depending on who you're talking to...
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