How's the weather at Diwali?
Keeping Gregorian calendar in mind Diwali falls in the month of October or November and keeping Hindu Lunar calendar in mind it is celebrated in Kartik.
It is commended for about 5 days. It is a time when winters are about to start.
The weather is yet warm and October heat is still on. Bursting of fire crackers make the environment even more warm.
In North India temperature is high during day and drops as the sun starts to set. In the Mountains weather is very cold.
In the south one can expect some rain as the south east monsoons hit the coasts during this time. No matter what ever the weather is the celebrations go on in full swings.