Patna is characterized by the presence of three distinct seasons - Summer season, Rainy season and Winter season. It has a humid subtropical climate with hot summer, moderate rainfall and mild winter.
Summer : Summer marks its beginning in the month of March and stretches till June early, till the arrival of the monsoon. The summer is hot and humid. The temperature in Patna can go up to 43 °C during day at the peak season, whereas the minimum temperature stays around 21 °C. The Sun rises early in the morning and stays till late evening. As the Sun rises, the temperature rises. At around 2 PM, maximum heat is felt. Due to humidity, sweating is common. A striking feature of the summer season is the 'Loo'. These are strong, gusty, hot, dry winds blowing during the day. Sometime they even continue until late in the evening. Generally by evening, heat goes but humid condition remains, though it becomes cool outside. Dust storm is common during the month of May. They provide temporary relief as they lower the temperature and bring light rain and cool breeze. The city also experiences localized thunder-storms and dust raising winds. The highest ever recorded temperature is 46.6 °C during 1996.
Monsoon : The monsoon generally arrives in Patna around 10th June. Its arrival gives relief to the scorched-land and people burning with heat. Within hours, the black clouds covers the entire sky and suddenly the bright day starts looking as dark evening. The dusty storm rises and fill the sky with dust. The first rain cools down the temperature and brings cheer to the people. The monsoon season stays till September, however Patna receives most of the rainfall during the month of July and August. The arrival of monsoon gives relief from heat, but not from humidity. As the humidity increases, it make harder for the people to bear it. The rainy season heat is also very strong, but it does not remains for longer time. The city receives approximately 100-120 cm of rain during a normal monsoon. The highest rainfall ever recorded was 204.5 cm during 1997.
Winter : By the time monsoon retreats, the city gets a pleasant weather, waiting for winter to arrive. The season roughly extend from October to February, however December to January are the coldest months. The winter season is also the best time for visitors to explore the city and to witness the series of festivals. The temperature of Patna varies around 20 °C during the day. At night, it becomes colder. During January, heavy fog can be experienced, dense enough to disrupt the normal life. Most of the flights gets either cancelled or diverted during such conditions. Most of the trains runs late due to heavy fog in the Gangetic plain. A light rain brought about by the westerly disturbances in such conditions makes the temperature even lower. The Sun rises late and sets early. The days are short and nights are long during the period. The lowest ever temperature recorded is 1.1 °C on January 2013.