Heavy rains which occurred in Uttarakhand's Dehradun on Monday night "cannot be defined as a cloudburst", Head of India Meteorological Centre, Dehradun, said. "This comes under the category of an extreme, intense spell of rain," said Dr Chander Singh Tomar. Interaction between easterlies (east-west winds) and westerlies (west-east winds) or air masses over the region leads to rainfall, he said.