Because of its location in southern Asia, India experiences unique seasons which are based around a dry summer and an extremely wet monsoon season. India is roughly half the size of the U.S., which means that there is no overall climate for the country. In the south the climate is warmer and drier than the more temperate north. The terrain ranges from permanent snow fields to tropical coastlines and from the mountainous Himalayas to low lying plains around the Ganges river.
The Indian Meteorological Service divides the year into four seasons: a cool and dry winter from December to February, a hot and dry summer from March to May, monsoon season from June to September and a retreating monsoon season in October and November. In contrast to parts of the U.S. which experience an even spread of rainfall across the year, India experiences around 80 percent of its rainfall in just a few months. This is due to the dominance of the Asiatic monsoon wind system which brings almost constant, torrential rain to much of the country for several months each year.
Because of its large size there is no overall average temperature for the country. In Srinagar, located in the north of the country, the average summer temperature ranges from around 11 degrees C (51 F) to 25 degrees C (77 F). In mid region of the country, in Hyderabad, temperatures in summer can range from around 20 degrees C (68 F) to 44 degrees C (111 F) with stifling humidity due to the monsoon rains. In the southern city of Chennai summer temperatures range from 26 degrees C (78 F) to 40 degrees C (104 F) with similar levels of humidity to Hyderabad.
For around six months a year most of India experiences little rainfall. Some areas in the south will see no rainfall at all during this dry period. The cities that experience the most rain are situated in the north; Delhi and Kolkata generally receive under an inch of rain in January to March. This amount of rain is similar to the amount in Arizona early in the year.
In contrast to its dry season, India experiences an extreme wet period known as its monsoon season. At the peak of the season in September, cities across the country experience an average 8 inches of rain. Monsoon rains carried by the Asiatic wind system generally travel across the country from the southeast to the northwest, but are known to reverse direction for some months, traveling from the northeast. The usual southeast to northwest monsoons begin at the start of June in Tamil Nadu, reaching Kajasthan around the start of August.
Also known as retreating monsoon season, this is when the main bulk of rain has fallen and the country slowly returns to a dry period. The post-monsoon season is gradual and covers several months, whereas the onset of monsoon season is much quicker. During this period rain falls roughly half as much each month until December.