Prices for used cabriolets have traditionally risen during spring and summer and then fallen as daylight hours shorten.
Jeff Paterson, senior car editor at Glass's Information Services, said: 'Although cabriolet sales remain higher during the spring and summer months, motorists are no longer looking to abandon them simply because autumn and winter set in.'
He points to improvements in hood technology, wider availability of hardtops and higher levels of build quality as key factors in bolstering cabriolet sales.
Paterson added: 'We are finding that values are stabilising as more buyers realise they can run a modern cabriolet as a practical vehicle that is perfectly able to keep out the very worst of the British weather.'
Part of the reason is the wider availability of folding hard-tops, such as on the Peugeot 206 CC and Mercedes-Benz SLK.