Weather in India in September is a mixed bag. Whilst the heavy monsoonal downpours of July and August have tailed off, rainfall should still be expected throughout much of the country, especially in Kerala, Darjeeling and Mumbai. Rajasthan is the pick of the bunch at this time of year: rainfall is minimal, humidity levels are low and daytime temperatures hover around 30°C.
September's weather in the far north of India is a mixed bag. The monsoon rains are drawing to a close towards the end of the month but you're likely to experience a few rainy days. The exception is Srinagar which remains virtually dry. You can expect plenty of sunshine and pleasantly warm temperatures just about everywhere too. So, it's not a bad month to visit.
The weather in September in Goa, Kerala and Tamil Nadu is usually good. The south west monsoon is nearing its end in the east coast states of Kerala and Goa, whilst the returning monsoon which drops rain on Tamil Nadu is a month or so away. Temperatures are pleasantly hot: ideal for relaxing on the beach, exploring ancient temples, trekking through national parks and pootling around the backwaters on a houseboat.
September weather in Mumbai and the rest of central India is a mixed bag. The monsoon rains draw to a close towards the end of the month but you're bound to experience some rainy days. If you don't mind dodging the showers, the rural scenery is particularly impressive after all the rain: lush green and strewn with flowers.
You won't be disappointed if you visit Rajasthan and the north in September. The monsoon rains are almost over, the countryside is brilliantly green and temperatures are cooler than the baking months of May and June. Culture fans will love the festivals that take place at this time of year, offering unique insights into local life. You should pack a brolly but chances are you won't actually use it that much.