October is a great time to visit Cyprus. Expect temperatures in the mid 20's with warm sunny days but cooler evenings (around 18-20 degrees C)
For clothing, bring a mix of summerwear for the day and some light sweaters/fleeces/trousers for the evening. You will probably find the evenings warm by UK standards though we are wearing jackets/sweaters by then!
Sea temperatures are still very warm in the mid 20's after the August summer heat so lots of opportunities for swimming. If you plan to visit the Troodos mountains you will need warmer clothing for the evening as temperatures are around 5 degrees cooler than on the coast.
