Over the past four decades, global warming has taken hold in Portugal according to statistics gathered by the Instituto Português do Mar e da Atmosfera ‑ IPMA. Maximum temperatures have increased by 1.6ºc over the past 40 years and summer has stretched by 6 more weeks in the north and centre of the country, as defined by the number of days with temperatures above 25ºc. This trend has been less pronounced in the south. There has also been less rain leading to more frequent severe droughts.