Climate plays a key factor in deciding when to visit India. Keep in mind that climatic conditions in the far north are distinctly different to those of the extreme south. Generally, India's climate is defined by three seasons - the hot, the wet (monsoon) and the cool, each of which can vary in duration from north to south. The most pleasant time to visit most places is during the cooler period: November to around mid-February. The heat starts to build up on India's northern plains from around February, and by April or May it really hots up, peaking in June. In central India temperatures of 45°C and above are commonplace. South India also becomes uncomfortably hot during this time.

Late in May the first signs of the monsoon are visible in some areas - high humidity, electrical storms, short rainstorms and dust storms that turn day into night. The hot season is the time to abandon the plains and head for the cooler hills, and this is when hill stations are at their best (and busiest). When the monsoon finally arrives the rain comes in steadily, generally starting around 1 June in the extreme south and sweeping north to cover the whole country by early July.

The main monsoon comes from the southwest, but the southeast coast (and southern Kerala) is largely affected by the short and surprisingly wet northeast monsoon, which brings rain from around October to early December. Things don't really cool down: at first hot, dry and dusty weather is simply replaced by hot, humid and muddy conditions. It doesn't rain all day, but it rains every day. Followed by the sun this creates a fatiguing steam bath-like environment. Around October the monsoon ends for most of the country. This is when India sees most tourists - however, it's too late to visit Ladakh (May to October is the optimum period).

During October and November it's generally not too hot and not too cool (October can still be humid in some regions). In the thick of winter (around mid-December to mid-January), Delhi and other northern cities can become astonishingly cold, especially at night - and it's bone-chilling in the far north. In the far south the temperatures become comfortably warm during this period.