Summer in Pamplona tends to be hot and dry, but summer storms can occur and when it rains it rains with a vengeance. Temperatures can dropdramatically then and the days can be cool. Maybe, between 10 and 15 degrees Celsius. Other days can be extremely hot, up to 40degrees coleus. It depends on the year. Whatever the weather is like during the day, the nights are always a bit cool, particularly those dark hours just before dawn. This is the time when many a reveller is inadvertently parading from bar to bar in light dress oblivious to the change in temperature. The consequences of which will appear a day or two later in the form of colds, flu, and hoarseness etc. So, take a jersey or pullover for the nights and remember to bring some rainwear, just in case.