Under the Köppen climate classification, City of Thrissur features a Tropical monsoon climate. Since the region lies in the south western coastal state of Kerala, the climate is tropical, with only minor differences in temperatures between day and night, as well as over the year. Summer lasts from March to May, and is followed by the South-west monsoon from June to September. October and November form the post monsoon or retreating monsoon season. Winter from December through February is slightly cooler, and windy, due to winds from the Western Ghats.
The City is drained in the monsoonal season by heavy showers. The average annual rainfall is 3000 mm. The South-west monsoon generally sets in during the last week of May. After July the rainfall decreases. On an average, there are 124 rainy days in a year. The maximum average temperature of the City in the summer season is 33 degree Celsius while the minimum temperature recorded is 22.5 degrees Celsius. The winter season records a maximum average of 29 degree Celsius and a minimum average of 20 degree Celsius
