00:00When it comes to predicting snow, a change in temperature of just one degree can mean the difference between this and this.
00:07But this small temperature change is also determined by other factors.
00:12The air tends to be colder on hilltops.
00:15A village at 300 metres may be cut off by snow, whilst a neighbouring village at sea level just gets rained on.
00:23Proximity to the sea also matters for an island nation like the UK.
00:28Seas and oceans have a moderating influence on climate, keeping us milder in the winter and cooler in the summer than would be the case if we were in the middle of a continent.
00:38Sometimes, just a few miles inland from the coast can be the difference between rain and snow.
00:45The intensity of the precipitation – rain, sleet or snow – is crucial.
00:50Water needs energy to evaporate, which it takes from the surrounding environment.
00:55That's why we feel colder when we're wet.
00:58Droplets of water on our skin evaporate and steal heat energy from our bodies.
01:04The same happens when it rains.
01:06Rain evaporates as it falls and takes heat out of the atmosphere.
01:10The longer and harder it rains, the more cooling takes place.
01:14If the temperature is already close to zero, enough cooling can result in snow.
01:19And what about the timing of the snow?
01:22If it arrives early in the morning following a frosty night, it can settle and disrupt the rush hour.
01:28A couple of hours later, the roads may have warmed up with the snow melting on impact.
01:33And of course, when snow arrives in the form of showers, just like rain showers, these can be very hit and miss.
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