This unusual sight, known as a hole punch cloud, or fallstreak hole, was snapped in Lincolnshire, but what is actually happening here?

This impressive and unusual formation seen in Boston appears as a gap, or hole in the surrounding cirrocumulus or altocumulus clouds.

These clouds are high enough, and consequently cold enough, to contain supercooled water droplets. These water droplets within the cloud are sub-zero, but not actually frozen.

So when aircraft pass through this cloud layer, it causes the surrounding air to expand and cool. The change in temperature can then cause the water droplets to suddenly freeze into solid ice crystals.

These ice crystals then fall from the sky as virga, or fallstreaks, which is precipitation that doesn’t reach the ground.

It might sound surprising, but the process of freezing actually gives off a tiny bit of heat. This heat is enough to evaporate the surrounding water droplets, leaving the sharply defined hole in the clouds that you can see in the image.