Uniqueness of seasons in Kerala – Implications on thermal stress and productivity of animals

Pattern of seasons in Kerala, with predominantly hot humid climate, has been found to be hostile for the enhancement of animal productivity. In the context of climate change, alterations and inconsistencies of the seasons has been reported worldwide. Hence, weather parameters of Kerala were studied over a period of six years with emphasis on the seasonality and causation of thermal stress in animals. The study was carried out at Livestock Research Station, Thiruvazhamkunnu. Ambient temperature (AbT) and humidity of six years were collected from Automatic weather stations (AWS) and Temperature Humidity Index (THI) was calculated using formula. The weather parameters were analysed for monthly, seasonal and yearly pattern and the findings are discussed. It is evident that summer season in Kerala (March to May) does not correspond to the entire long day period. Even though AbT and THI were increasing from January onwards with increasing day length, onset of raining in June causes sudden drop in AbT responsible for the peculiar Kerala climate. Climatic parameters in September were more similar to October-November (North-east monsoon) than June to August (South-west monsoon). Even though December to February (post monsoon) forms winter season in rest of the country, the lowest temperature recorded in the study was 18.3 ºC, making the term “winter” a misfit except for high ranges. Thus it appears that four quarters of three months each, designated as South-west monsoon, North-east monsoon, Post monsoon and Summer forms better classification of seasons in Kerala and THI was high enough to cause thermal stress throughout the year