People often talk about April showers and there's an old English folk rhyme that states: "March winds and April showers bring forth May flowers."
Showers can occur at any time but there are specific reasons why April might be more associated with clear, sunny mornings and stormy afternoons.
During spring, the Azores high pressure system and the polar jet stream tends to move further north.
The sun is also higher in the sky at this time of year and therefore stronger.
Consequently, temperatures rise and the ground heats up. As the warm air rises, it cools and condenses, forming clouds.
During April the air higher up in the atmosphere can be much colder than the air at ground level.
This causes the air to be unstable and clouds soon start to bubble up after a fine and sunny start to the day.
Cumulus clouds by Mike Davies.
While these clouds may be nothing more than 'cotton wool' clouds, they can sometimes develop into large cauliflowers of cumulus and towering cumulonimbus clouds - capable of producing heavy showers, hail and even thunder.
During an April shower, the temperature can also vary widely. When it’s sunny, the temperature in the shade can easily reach a warm 20°C.
However, a heavy shower with hail can see the temperature drop sharply to around 10°C.
As the sun sets the shower clouds will often fade away leaving a clear and chilly night.
