April showers

We often think of this old piece of weather lore during the spring months in the UK, but is there any truth in it?

What are showers?

Showers are sporadic bursts of rain coming from individual cumulus clouds. When the clouds have enough energy to grow big enough, they become cumulonimbus clouds, which give us thunderstorms. Showers and thunderstorms can result in a torrential downpour in one place, whilst remaining totally dry just down the road.

At this time of year in the UK we are in a transition period between the long, cold (well sometimes) Winter months, and the warmer Spring and Summer. The jet stream starts to move northwards, which can bring the first signs of warmth, but also tends to make our weather more unsettled due to low pressure systems being driven towards the UK, and so we get rain, showers and strong wind.

What causes showers?

But it isn't just low pressure that results in showers, they can also develop due to daytime heating. At this time of year, the sea temperature around the UK is at its lowest, meanwhile the heating we receive from the Sun is increasing as the Sun rises higher in the sky and daylight hours increase. This results in warm land temperatures compared with sea temperatures, and so shower clouds develop preferentially over the warmer land.

So there is some truth to the weather lore that April showers bring May flowers, as April does tend to be a showery month, and the warmth of May soon follows bringing the familiar colours of the UK spring.