NEW DELHI: Light jackets have given way to T-shirts in the span of a week as weather in the capital has transitioned unusually rapidly from late winter to summer this year. Delhi saw a whopping 13-degree rise in maximum temperatures in the past 10 days, with spring disappearing almost as soon as it arrived.Thursday's peak temperature was 37.4 degrees Celsius, seven notches above normal - the highest seen in March since 2010, when the mercury had hit 39.2 degrees on March 22. Just 10 days ago, the maximum had hovered around 24 degrees. Similarly, minimum temperatures have risen by around 9 degrees in this period.Such a rapid transition to summer is rather unusual. The change has been all too sudden also because below normal temperatures prevailed till well after Holi this year, under the influence of a series of active western disturbances that brought rain and snow in the hills.“That influence has waned. At the same time, a wind pattern has formed that's causing heating in the northern plains," said Ravinder Vishen, head of IMD's Regional Weather Forecasting Centre. Met officials said, with the summer wind patterns now in place, temperatures are expected to climb in the coming days. By next week, peak temperatures in the capital could climb close to 40 degrees Celsius.“Wind circulation features at the moment suggest that the summer season has begun,“ said IMD spokesperson K Sathi Devi.The cause of the heating is an upper air zone of high pressure, called a ridge, over Rajasthan and parts of central India. “Due to this, there is a downward movement of air, which is leading to temperatures way higher than normal in northern India," said Vishen.The heat is in line with IMD's seasonal forecast for March and April that said average temperatures may be one degree above normal in northern India. The forecast was based on IMD's computer models that take into account global features such as the current heating up of the Pacific Ocean. Being a transition month, March sees a large variation in weather patterns. Last year, for example, the month began on a very hot note. Maximum temperatures were around 31-32 degrees C. The month ended at around 37 degrees. Thus, the variation in peak temperatures was just around 6-7 degrees.In 2015, the variation was much larger - around 16-17 degrees C over the 31-day period. The previous year, 2014, showed an altogether different pattern. Maximum temperatures in the beginning of the month were around 21 degrees C while the month-end temperatures were in the 30-31 degree range.