Mom Said "It's Too Cold To Snow"
Today we received our first light snow mixed with rain. It also brought back the memory of Mom always telling us when it got really cold and we wanted snow to play in she would say "It's too cold to snow" I decided today to find out if that is true and by gosh it is!! Mom was very smart and also was full of common sense!
The question deals with snow and temperature, specifically asking does it ever get too cold to snow? Many people have told me they are sure that once the temperatures get around 0 degrees Fahrenheit it is too cold to snow. But is this true?
For most places on Earth, the heaviest snows occur when temperatures are close to freezing, even a degree or two above freezing. This is because warmer air can hold more moisture than colder air. Since the atmosphere must have moisture in it to generate snow, if it gets too cold there may not be enough moisture for snow to form.
Most clouds form through a process called expansion cooling. A mass of air will rise which causes it to expand because of the lower atmospheric pressure. When the air mass expands, it also cools which in turn reduces the amount of water vapour it can contain. This excess water vapour condenses out into a cloud.
When air temperatures are already pretty cold, this expansion cooling process starts in air that already has a low level of water vapour. This means that clouds that form at colder temperatures, if they form at all, have much less water vapour (in the form of ice crystals,) in them. Snow needs those ice crystals to begin forming.
When the temperature is cool, but not too cool, the ice crystals will begin to bond together and create snowflakes. Again, if it is too cold, the ice crystals will not bond, but remain solitary crystals, called ice needles. There is no low temperature limit for ice crystals to form, it is only their bonding which is limited by temperature. Such a deposit of ice needles is rare in our area, but in the Arctic it is called ice fog.
So yes, it can get too cold to snow but it has to be really cold. Once the air temperature at ground level drops below about -10 degrees Fahrenheit (-20 degrees Celsius,) in most places, it becomes very unlikely that snow will fall. It can snow at 0 degrees Fahrenheit, it's just that it won't snow a lot. So, if you don't like snow, you need to hope for colder temperatures!
The question deals with snow and temperature, specifically asking does it ever get too cold to snow? Many people have told me they are sure that once the temperatures get around 0 degrees Fahrenheit it is too cold to snow. But is this true?
For most places on Earth, the heaviest snows occur when temperatures are close to freezing, even a degree or two above freezing. This is because warmer air can hold more moisture than colder air. Since the atmosphere must have moisture in it to generate snow, if it gets too cold there may not be enough moisture for snow to form.
Most clouds form through a process called expansion cooling. A mass of air will rise which causes it to expand because of the lower atmospheric pressure. When the air mass expands, it also cools which in turn reduces the amount of water vapour it can contain. This excess water vapour condenses out into a cloud.
When air temperatures are already pretty cold, this expansion cooling process starts in air that already has a low level of water vapour. This means that clouds that form at colder temperatures, if they form at all, have much less water vapour (in the form of ice crystals,) in them. Snow needs those ice crystals to begin forming.
When the temperature is cool, but not too cool, the ice crystals will begin to bond together and create snowflakes. Again, if it is too cold, the ice crystals will not bond, but remain solitary crystals, called ice needles. There is no low temperature limit for ice crystals to form, it is only their bonding which is limited by temperature. Such a deposit of ice needles is rare in our area, but in the Arctic it is called ice fog.
So yes, it can get too cold to snow but it has to be really cold. Once the air temperature at ground level drops below about -10 degrees Fahrenheit (-20 degrees Celsius,) in most places, it becomes very unlikely that snow will fall. It can snow at 0 degrees Fahrenheit, it's just that it won't snow a lot. So, if you don't like snow, you need to hope for colder temperatures!
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