Difference between sleet and freezing rain

In places where the climate remains very cold throughout the year with temperatures being consistently negative, it is quite common to come across various forms of precipitation. The two most common words used to describe these natural phenomenon include rainfall and snowfall. Although most of the time, these precipitations are either rain on snow, it is not always that the falling drops are merely liquid (rain) or flakes of ice (snow). It has been noticed that sometimes the rain that falls to the ground freezes as soon as it meets any surface. Sometimes what falls from the clouds are indeed ice pellets but not snow. To best explain these slightly differing phenomenon, we use other words such as sleet, freezing rain, hail etc.

To begin with, freezing rain is merely normal rain when it is falling from the clouds to the surface. It falls as tiny water droplets. However, what makes it different to normal rain is the fact that it droplets freeze as soon as they meet a surface. Since the temperature on or slightly above the Earth’s surface is about 20-30 degrees centigrade, and in any case, higher than the temperature high up in the atmosphere, the droplets freeze on hitting roads, buildings, trees etc. Sleet is not the same as freezing rain. The precipitation that falls in the form of ice pellets is termed as sleet. In simpler words, the word sleet incorporates those small ice pellets that are seen to be bouncing off our windows, windshields or the ground. It maintains its solid, icy consistency on touching the ground and usually accumulates the same way as snow would.

Both of these precipitations occur in the winter. But the question is that what causes these different precipitations? Where temperatures are below zero, the falling snow passes through a warm layer where the snowflakes melt to become the water droplets that we call rain droplets. These droplets fall to the ground and re-convert into pellets on touching any surface. In the case of sleet, the beginning part remains the same, that is, snow that is falling passes through a warm layer and converts into rain droplets. However, as these drops fall, owing to their path through a cold-layer of freezing or sub-freezing air close to the Earth’s surface, they refreeze into the ice pellets once again before falling to the ground.

The warm layer that we talk about where snow is converted to freezing rain or sleet is a bit different for both cases. For snow to be converted into freezing rain, the warm layer needs to be deeper and extends close to the ground, which in turn makes the sub-freezing layer near the Earth’s surface thinner than before. This is the reason that the newly formed rain droplets do not have much time to refreeze into ice pellets before falling to the ground as in the case of sleet. They usually reach the ground by the time they refreeze and would refreeze on touching a surface anyways. As for sleet, the warm layer is higher up in the atmosphere so the droplets that emerge from this layer have sufficient time to refreeze before falling to the ground and hence form sleet.

There are also some differences in how the two appear and their consistency as they fall to the ground. Freezing rain is usually just water droplets in the liquid state but at a very low temperature, as if they are just about to freeze anytime. In contrast, sleet that falls in the form of tiny ice pellets is actually a mixture of snowflakes and rain droplets.

Summary of differences expressed in points

1. Both are forms of precipitation; sleet-ice pellets or small flakes of snow as in snowfall; freezing rain-similar to droplets in rain but freeze on contact with any surface
2. Freezing rain- formed when falling snow passes through a warm layer, droplets are formed; sleet – forms when snow passes through a warm layer, droplets are formed, droplets converted into ice pellets before reaching the surface
3. The warm layers in both the phenomenon are different; sleet, warm layer high in atmosphere; freezing rain- warm layer quite low, droplets do not have much time to freeze before reaching the ground
4. Freezing rain-just water droplets; sleet- mixture of snow and rain droplets

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