As seen in the chart, the coldest months are December, January and February; and the hottest months are April, May and June. Apart from this, it is also prudent to check the rainy season – which starts in June and ends in September, with the months of July and August experiencing the heaviest rainfall.
These statistics are compiled from the previous years' averages. But in this age of erratic weather believed to have been brought about by global warming, Jaipur too has been witnessing ever changing climatic conditions. Some locals even say that they had just experienced the coldest and longest winter of their life in Jaipur at the beginning of this year.
Therefore it is a good idea to check updated forecasts for the weather at this website: http://www.wunderground.com/global/stations/42348.html