Read the following context and answer the question.
Context: And looking out of the windscreen , we saw something I ' ve never seen before : a sort of limp sausage - shaped cloud sticking out of the side of a thunderhead , hanging down towards the Shannon Estuary . It looked like a cloud with a ponytail . Odd thing . The twisting of the tip hanging down made it more obvious , though : it was a tornado !
Question: What may have caused the tornado ?
Answer:


They were having a storm while it was hot outside .