When travelling, we recommend packing in preparation to handle common weather conditions. The rainfall in Chennai is typically less than Trondheim. We can gather that this will continue over the next 2 days.
You can imagine temperatures to be in the 38 °C range in May. The weather in Trondheim is generally colder than Chennai's. As flight availability is subject to become more limited as peak season approaches it is ideal to book in a timely manner.