4 Apr 2016

What causes April showers?

As I walked to the train station this morning on the way to the newsroom, I looked up at the sky to be greeted by a classic April showers cloudscape.

The warmth of the increasingly strong spring sunshine on my face was punctuated by puffy cumulus clouds temporarily throwing some shade, before the sun returned moments later.

April is a time of year when the weather can vary hugely across the UK – from bursts of warmth, to late season snowfall, but one thing we are all familiar with is April showers.

Rainbow over Dingle on Christmas day

We’ve all been there; heading out at lunchtime in the sunshine to get a sandwich, only to get caught in a spectacular downpour as a big shower seemingly appears out of nowhere.

But what causes April showers and why are they most common at this time of year?

Big temperature contrasts

In the world of weather, the three main drivers are contrasts in temperature, pressure and humidity, with the general rule that the bigger the contrast, the more dramatic the resultant weather.

Spring heralds a time of year when there can still be significant temperature contrasts across the UK, as Sweeping Barleyfield Landscapebursts of cold air contrast with the warmth of the increasingly strong spring sunshine.

Temperature contrasts are not just important on the ground itself, but also between the ground and high up in the atmosphere – something known as the lapse rate.

The greater this difference in temperature between the ground and high up in the atmosphere, the more unstable the air becomes and the more readily it wants to rise upwards, forming clouds and showers.

And, with April being a time of year when this vertical difference in temperature is significant, it is a time of year when (April) showers are most prevalent.

Great cloudscapes

The month of April can provide some great cloudscapes when looking up, as clouds of all shapes and sizes roam the skies.

From innocent looking cumulus clouds, to threatening towering cumulus or even the biggest of them all – cumulonimbus – the chaotic arrangement of clouds at different heights can bounce light around, making the sky look particularly dramatic.

Post rain.........There’s also the prevalence of rainbows, as sunlight hits the raindrops in the showers, reflecting and refracting the light inside each drop, splitting white light into the colours of the rainbow and projecting it across the sky.

So, with a week of classic April showers ahead, take a moment to pause and look up at the sky and see what’s up there. You may be surprised at the stunning scenes that you see – especially at sunset.

If you managed to capture any great pictures, then you can share them with me on Twitter and I’ll retweet the best ones – @liamdutton

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