The city has four distinct seasons and is in plant hardiness zone 3b. Saskatoon has a dry climate and sees of precipitation per year on average, with the summer being the wettest season. Saskatoon is sunnier than average in Canada as a result, averaging 2,268 hours of bright sunshine annually. The extreme temperatures are typically accompanied by below average levels of humidity. Thunderstorms are common in the summer months and can be severe with torrential rain, hail, high winds, intense lightning and, on rare occasion, tornadoes. The frost-free growing season lasts from 21 May to 15 September, but due to Saskatoon's northerly location, damaging frosts have occurred as late as June 14 and again as early as August. The average daytime high temperature peaks at from July 31 to August 8.