It is now official. The India Meteorological Department (IMD) on Saturday declared 2009 the warmest year since 1901, the year it started keeping records of temperatures and other weather parameters.

The average annual mean temperature over the country as a whole for the year was almost one degree Celsius above the average for the entire century -- plus 0.913 degrees Celsius to be precise.

The average of temperatures between 1961 and 1990 is considered as the benchmark. The average annual mean for the 30 years is 24.64 degrees Celsius. The average mean temperature in 2009 has been calculated to be 25.553 degree Celsius.

Earlier records were: +0.708 (in 2002), +0.6 (in 2006), +0.560 (in 2003), +0.553 (in 2007), +0.515 (in 2004), +0.514 (in 1998)), +0.448 (in 1941), +0.445 (in 1999), +0.435 (in 1958), +0.429 (in 2001), +0.413 (in 1987) and +0.410 (in 2005).

In a report published on its website, the IMD also said that trend analysis of mean temperature for different seasons -- winter (January to February), pre-monsoon (March to May), monsoon (June to September) and post-monsoon (October to December) -- showed that the winter and monsoon seasons in 2009 were the warmest.

The IMD has also analysed the spatial pattern of trends in mean annual temperature anomalies for 2009, and the study suggests a significant increasing trend over most parts of the country except some parts of Rajasthan, Gujarat and Bihar.

On a month-wise basis, mean monthly temperature over India as a whole was the highest since 1901 for January (+1.43 degrees Celsius) and August (+1.00 degrees Celsius), and the second highest for February, September and December.

More significantly, the positive anomaly was found to be highest for the maximum and minimum temperatures individually as well, apart from the mean temperatures, for the months of January, August and September in 2009, when the figures were compared over the previous five years — 2005 to 2009.

As the report recapitulates, abnormally warm conditions prevailed over major parts of the country during January-February last year. The temperature over hilly regions of the western Himalayas was three to five degrees Celsius above normal in the second fortnight of January, while in February the mean temperature over almost the whole country was above normal. There were, however, cold wave conditions on few occasions in Uttar Pradesh in January, causing the loss of about 80 lives.

Heat wave conditions (defined as the maximum temperature exceeding the normal by five degrees Celsius) prevailed on many occasions over the peninsular/central parts during the first three weeks of March, and over different parts of the country during April and the second and third week of May. About 150 deaths due to the heat wave were reported in May, mainly in Andhra Pradesh.