Follow Nick Trend's guide to discover the season's sunniest destinations.

I'm writing this in a hotel room in Siena. The sky outside is a luminous blue and a powerful heat haze is shimmering above the terracotta roof tiles of the medieval city. This afternoon the mercury hit 28C. If it weren't for the cooler evenings, you would think it was still midsummer. In fact it is September 13.

There are lots of good reasons to travel in the autumn. The summer crowds are dying down, prices are dropping sharply from the high-season peaks and in many parts of Europe the warm weather will last for several more weeks.

But travellers and sun-seekers for whom good weather is important have to be careful about timing. Leave it too late and there is a risk that the weather will break and your stay will coincide with a cool, damp spell.

It isn't simply a question of heading as far south as you can. For example, although it is a little further north, the Côte d'Azur has a warmer and sunnier autumn than the Costa Brava. And while Sicily and Corfu are both in roughly the same latitude, Sicily enjoys a much warmer, drier and longer season.

There are no absolute guidelines, of course. Weather patterns around the Mediterranean are a little more stable than in Britain, but they can be fickle, too. The weather I am enjoying in Tuscany, for example, is about 3C warmer than average for the time of year.

But statistics are the best guide we have, so, based on those, here is an at-a-glance strategy for those who are looking for a last fix of summer sunshine before winter sets in. Travel before the deadline for each destination and you can expect daily peaks of above 20C and at least six hours of sunshine a day. Figures given below are averages for October unless stated otherwise. Useful sources of weather information are at www.bbc.co.uk/weather and www.wunderground.com.

Before the end of September

September is normally lovely in both the Costa Brava in Spain and Corfu in Greece, but both destinations can see a sharp deterioration in October. Both stay reasonably warm (highs of about 22C), but the Costa Brava gets less sun (five hours a day) and Corfu sees the start of its very wet winter during October.

Before mid-October

The long days of sunshine can last right to the end of October in many parts of the Med, but the weather usually breaks at some point during the month. The safe bet is to travel in the early part of the month to destinations such as the Algarve (eight hours of sunshine and highs of 22C), the South of France (seven hours, 21C), Corsica (seven hours, 22C), Majorca and the Balearics (six hours, 23C) and Tuscany (six hours, 21C).

Before the end of October

Head a little further south or east and the summer weather should cling on until the end of October. Italy is one of the best bets, with warm weather and plenty of sun in most parts south of Naples, including the Amalfi coast (six hours, 22C), Puglia (similar) and Sicily (six hours, 25C), which often has good weather well into November.

In Spain, the Costa Blanca (six hours, 23C) and the Costa del Sol (seven hours, 23C) are good choices, while Andalusia in general has an excellent autumn climate.

Further east, Crete (six hours, 24C) and the southern Turkish coast (eight hours, 24C) involve a flight of up to four hours, but are among the best choices for warm weather later in the month.

Last of the summer sun

The longest summer in Europe by far is enjoyed by Cyprus. This month average highs are still in the 30s with 11 hours of sun. This drops only to 28C and nine hours in October, and November still has average highs of 22C and seven hours of sunshine a day. See James Bedding's article on pages 16-17 for advice on finding the unspoilt sides to the island away from the overdeveloped resorts.