Heat wave is generally synonymous with the pre-Monsoon season over the Indian sub-continent. Though we even see heat wave condition in October, post the withdrawal of Monsoon in some parts of the country particularly over Rajasthan and Gujarat.
During this period, winds change, humidity level drops and there is more sunshine. Rajasthan and Gujarat witness temperature exceeding forty degrees. Some parts of West Bengal like Midnapore and Kolkata to witness such weather conditions only if Monsoon withdraws early from this part of the country.
The prolonged absence of rain, the long prevalence of dry northwesterlies and thick dust suspension leads to heat wave conditions in North India. It is the criteria for fulfilling the heat wave condition during the Pre-Monsoon season.
Also, the month of March is very hot for Punjab, Haryana, Rajasthan, Uttar Pradesh, and Delhi. During this month, the mercury tends to cross forty degrees. A heat wave condition is declared when the mercury touches forty degrees along with the normal exceeding by five degrees.
In the Pre-Monsoon season as well, Rajasthan and Gujarat witness temperature in the range of 40°C to 50°C. Some pockets of Odisha, Central Madhya Pradesh, Maharashtra, South Telangana, and Andhra Pradesh also tend to see heat wave conditions. Whereas during the Monsoon period, if the Monsoon is inactive for some time with partly cloudy to cloudy sky, then the mercury will not rise. Parts of Odisha and West Bengal will not heat up.
On the contrary, instances of heat wave conditions are very likely in Northwest India during the Monsoon season because the Monsoon current is very weak in Punjab and Haryana and the winds keep changing from easterlies to westerlies and vice versa.
For instance, on July 11, Palam recorded 40.6 degrees which is five degrees above normal and it completely suffices the condition to be called as a heat wave one.
The northeastern states of the country, coastal stations, and hill stations are the exceptions that don’t see heat wave conditions during this time.
In the Monsoon season, heat escapes from the places where the Monsoon current remains more prevalent. Like South Peninsular India during this time don’t see much of heat and chances are very bleak of the mercury touching forty degrees and similar is the case with Maharashtra as well.
Places like Hyderabad, Nagpur, Gulbarga, Bhubaneswar, Jamshedpur, Kolkata experience heat wave during pre-Monsoon season but in Monsoon they will not touch the mark of forty degrees. While Lucknow, Meerut, and Kanpur touch 40 degrees.
This is not the case with Gujarat during Monsoon however freak incidences cannot be ignored. Bhuj, Naliya, Vadodara will not see mercury soaring to forty degrees sans any rain/weather activity.
Image Credit: The Weather Channel
Please Note: Any information picked from here must be attributed to skymetweather.com