Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Kempegowda Intl to Mulhouse as you normally would.
The rainfall in Bangalore is generally more than the rainfall in Mulhouse. This will continue over the next 1 days.
You can imagine temperatures to be in the 34 °C range in April. The weather in Mulhouse is generally colder than Bangalore's. As flight availability is subject to become more limited as peak season approaches it is ideal to book in a timely manner.