Warm night is a geographical phenomenon mostly happens in sub-tropical areas. It is closely associated with heat wave condition. In warm night maximum diurnal temperature touches 40 degree Celsius and above. Also minimum temperature must be above 4.5 degrees Celsius above normal.
It mostly occurs at indo gangatic plains of India during the summer season. It feels day like warm to us. It is very harmful for human health.
The major reason behind occurrence of warm night is the soil acts as a ‘sink’ for heat, absorbing sunlight during the sunny morning and afternoon hours and releasing it into the atmosphere at night. Greenhouse effect is also contributed to this.