When to visit Rishikesh and what to wear
Weather in Rishikesh
The best months to visit Rishikesh are mid-September to end-November and mid-February to end-April.
Starting from December and throughout January, Rishikesh can be quite a cold place (though not every year), which can be especially unpleasant due to the absence of heating in rooms and yoga halls. Since May Rishikesh becomes intensely hot, and in combination with heightened humidity this heat provides interesting opportunities for practicing equanimity in increasingly unpleasant and almost miserable conditions. Again, the start and end of each season vary year to year, but the weather tendencies have been more or less similar.
If you want to go to Rishikesh as an independent traveler, you need to take into account the fact that many yoga teachers plan their foreign travels and retreats for the out-of-season months (may to September and mid-December to January). So even if you have no other options than to visit Rishikesh during these months, you might miss most interesting teachers. Unless, of course, you have signed up to their course, in which case they will have to stay in Rishikesh and suffer the inconveniences with you.
Clothing advice for Rishikesh
During the season, the rainy days are very rare. Therefore I advise to bring light clothes, but women should make sure that their attire covers their shoulders and knees, to avoid unnecessary intrusive attention from Indian men. Since you are likely to visit many chillout places, a skirt would not be as comfortable as light pants, or even better Indian Alladin style pants which you can get in stores of Rishikesh for s about 200 rupees. Some light jacket or pullover will also be useful.
It’s a good idea to take UV-filter cream and sunglasses, as the sun in India is very strong, especially in from April to October.
It is customary in India to take off your shoes before entering a temple, someone’s home, place of practice, yoga hall, and many chillout cafes. Since you, therefore, will need to frequently take off and put on your shoes, running shoes and other laced shoes would not be as comfortable as sandals, flip-flops, crocs, and flats (ballet shoes). I have seen a couple of girls come to Rishikesh in high heel shoes. Don't do it. Rishikesh is not a city but quite a dusty village. You will just twist your ankles and look out of place among people in flip flops and crocs.
Also, you can take with you a shawl, or buy it in Rishikesh. It’s a simple and universal thing that can serve many purposes: protection from the cold or the sun, a bathing suit on Ganga (girls are not advised to bathe in Ganga in western swimsuits, it’s again the norms of decency in India (outside Goa perhaps) and attract lots of undesired attention), a pillow cover, if you find the bedsheets in your room of dubious freshness. Some minimalists even use the shawl as a towel.