Basically, it’s a question of when not to go to the Himalayas. The depth of winter (December to February) is best avoided because of freezing temperatures.
It’s not unknown for foreigners to visit at this time of year, but you’ll need a good line in thermal jackets.
The monsoon (June to September) can make trekking unpleasant – not least because the clouds will obscure the views — but not unbearable.
