The Best Travel Time? It Doesn't Exist. But the Worst Does.
Everyone looks for the perfect weather window. There isn't one. There are only better and worse compromises — and those who understand how monsoons, dry seasons, and altitudes work ride more relaxed.
The worst thing: visiting a destination at the wrong time. Morocco in August at 47 degrees. Vietnam during the monsoon. Patagonia in the austral winter. That's not adventure. That's punishment.

October to March: The Time for South America
Patagonia is ridden from November to March. Period. The austral summer brings long days, pleasant temperatures between 10 and 20 degrees, and winds that are still manageable.
The motorcycle journey through South Patagonia — from Bariloche to Ushuaia — covers this in 15 days: glaciers, steppe, gravel, and sky wider than anywhere else on earth.
Important: in Patagonia a storm rolls in within two hours. Plan buffer days — not for sightseeing, for storm breaks.

October to April: North Africa and the Sahara
Morocco in March is almost perfect. The passes in the High Atlas still have snow at the top but are passable. The valleys are green. The Sahara in the south sits at 25 degrees.
The enduro tour through Tunisia's Sahara works from October to March — then temperatures in the desert are bearable, the dunes are well-formed, the nights cold but not dangerous.

November to February: India and Southeast Asia
India works in two phases: October to February for the north and December to March for the south. The monsoon ends. Temperatures drop to a pleasant 20–28 degrees.
The Royal Enfield tour through Rajasthan takes 15 days and shows an India that has little to do with asphalt.
Vietnam, Thailand and Cambodia ride well from November to March. In April temperatures in Thailand climb above 40 degrees.
June to September: Europe and Central Asia
The Alps open their passes from mid-May. June and September belong to motorcyclists — July and August bring tourist convoys.
Central Asia — Kyrgyzstan, Tajikistan, the Pamir — is only rideable from June to September. The window is small. Use it.
Temperatures in Central Asia are a daily surprise: 32 degrees in the valley, 8 degrees on the pass, 25 degrees in the evening. The layering system works.
One Last Honest Thought on Timing
The best travel time is the one when you can ride. Not the one stated in this article.
Off-season has real advantages: fewer people, cheaper accommodation, more authentic encounters. Those who ride Morocco in October instead of March find markets without mass tourism and roads without tour buses.
Every destination in this guide has a peak season and an off-season. Which you choose depends on you — not on a season calendar.