Season decides more about a trip than destination does. The same place in the right and wrong month is two experiences, and in several cases one of them is not possible at all.
The fixed facts worth knowing
Southern hemisphere seasons are inverted. Summer is December to February in Patagonia, Australia, New Zealand and southern Africa.
Tropical regions have wet and dry seasons rather than warm and cold, and the dry season is usually the travel season.
Two dry seasons can be opposite within one region. Southeast Asia’s mainland is dry November to March; Indonesia is dry May to September. Thailand’s two coasts run opposite to each other.
One country can be three climates. Vietnam’s north, centre and south are never all good at once.
Altitude beats latitude. The Andes and the Himalaya have their own seasons unrelated to the lowlands beneath them.
Roughly, by month
January–February. Southeast Asia at its best. Patagonia and New Zealand in high summer. India in its cool dry season. Serengeti calving. Northern Europe cheap, dark and quiet.
March–April. Japan’s cherry blossom. Jordan and Morocco at their best. Victoria Falls at peak flow. Southeast Asia getting very hot.
May–June. The best months in western Europe and the Mediterranean. Nepal’s second trekking window. East Africa’s long rains ending.
July–August. Southern Africa’s dry-season safari peak. Scandinavia, the Baltics, Iceland and the Faroes. Ladakh and the Indian Himalaya. Mediterranean Europe hot and full.
September–October. Arguably the best two months on earth for travel: Europe still warm and emptying, Japan’s autumn beginning, Peru dry, Nepal’s clearest trekking, and Turkey and the Caucasus perfect.
November–December. Southeast Asia’s dry season opening. Patagonia opening. India cool. Northern Europe’s Christmas markets. The Serengeti moving south.
The seasons to avoid
Monsoon across South and Southeast Asia, June to September, except in the rain-shadow areas — Ladakh and Mustang — where it is the only season.
Atlantic hurricane season, June to November, peaking September, across the Caribbean and Central America’s east coast.
Pacific typhoons, roughly July to October, affecting Japan, the Philippines and Vietnam’s coast.
Northern Australia’s wet, November to April.
Patagonia’s winter, April to October, when most of it closes.
The shoulder argument
The months either side of peak — May and September–October in the northern hemisphere, November and March in Patagonia — are consistently the best value: most of the weather, a fraction of the crowd, and 30 to 50 per cent lower prices.
For places under visitor pressure, going in the shoulder is also the most useful single thing a traveller can do. See travelling responsibly.
Festivals and closures worth planning around
Ramadan shifts eleven days earlier each year and changes the rhythm of daily life across Muslim-majority countries.
Chinese New Year, Japan’s Golden Week and Obon, and Korea’s Chuseok each put hundreds of millions of people on the move and make everything unbookable.
August in southern Europe, when the countries themselves go on holiday and many businesses close.