Does it ever get too cold to snow?
Recent Chicago weather, huh? I guess this one has been on ice awhile–it arrived January 5, 2001. However, when a question is pegged to a Chicago cold spell, it’s not like if you miss one you’ve blown your last shot. Can it be too cold to snow? People from warm climates might be forgiven for thinking that’s a crazy question. After all, it only snows when it’s cold, so the colder it is, the snowier it must be. Right? Wrong. Arctic climates often get surprisingly little snow. Barrow, Alaska, for example, gets less snow than Chicago in an average year, despite having winters that average 39°F (22°C) colder. So does that mean it can be too cold to snow? Well, people from cold climates might be forgiven for thinking it can, since they have lived through a lot of cold winters and may have noticed that the coldest weather of any given year has never been associated with snow. That isn’t really because it’s too cold to snow, but because it’s too dry. (The coldest weather is almost always assoc
It’s a legitimate question that does have an answer. When the temperature outside is close to freezing, we see numerous large wet snowflakes. But as the mercury drops closer to 0F, the amount of water that the air can hold decreases. With the decreasing moisture, the snowflakes are much smaller and there are less of them. The snowflakes are now tiny individual snow crystals. Around -20F, the individual snow crystals become very fine and are hard to see. Snow is less common at this temperature. It typically stops snowing around -40 Celsius which is the same temperature as -40F. At this point, the air is simply too dry for the snow crystals and ice fog forms instead. This is when it officially becomes too cold to snow. There is not enough water vapor to produce the snow crystals in the arctic air mass. However, there are three ways that significant snowfall can occur at very cold temperatures as long as they are above -40F. If there is a strong enough lift, the air that is being lifted w
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,
Most precipitation that reaches the ground actually begins as snow high in the atmosphere. These snow flakes develop somewhere above the freezing level where … Since it is falling into cold air, the snow does not melt on the way down and reaches the ground as snow. This is why cold air is important for there to be snow.
