The climate of Saskatchewan is characterized by its extremes. Its position near the centre of the continent, a relatively high latitude, and great distance from the moist and moderating influence of oceans largely determine its atmospheric environment. It is generally considered a continental climate, with temperatures varying greatly between seasons. Precipitation is also variable both seasonally and inter-annually; average amounts are sufficient to support grasslands in the south and forests in the north. Extremes of temperature and precipitation are to be expected and form an integral component of the climate. Other factors are variable winds throughout the year, an abundance of sunshine, and possible severe weather in both summer and winter. The climate resources are usually sufficient for an agrarian economy, but sometimes impose constraints on these and other enterprises.
The temperature climate of Saskatchewan is extreme. It is common for temperatures at any point to vary more than 65°C within any year. The average values shown in Table CL-1 suggest a great seasonal variation but do not show the inherent variability. Latitudinal differences typically explain most of the 6–8°C difference in mean annual temperature across the province. However, extremes are still possible, no matter the latitude. The south Saskatchewan town of Midale had the highest temperature recorded in Canada at 45°C, and many sites have had record low temperatures of at least -50°C. These extremes of temperature are usually attributed to the province’s mid-continental position: the thermal character of the vast North American landmass heats and cools extremely well seasonally. It is also strongly influenced by the West Coast mountains, which inhibit the passage of moderating air from the west. The lack of terrain impediments to cold, Arctic air from the north is also a strong factor.
Saskatchewan has a relatively dry climate with a strong seasonal character. As with most mid-continental locations in mid latitudes, the majority of the precipitation is summer rainfall; but because of the coolness of winter temperatures, long-surviving snow pack is also an important factor. Year-to-year fluctuations in precipitation make for a challenging agricultural environment. The summer (May to September, inclusive) is the wet season, with usually two-thirds of the precipitation falling. Depending on the latitude, either June or July is the peak, with the more northerly locations having the later maximum. Most precipitation falls as a result of passing mid-latitude cyclones when their most favoured path crosses the region. Significant amounts can also result from convective systems (thunderstorms) at a variety of scales. Table CL-2 shows this seasonal character for stations spread across Saskatchewan.
Interannual variability is usually great. For example, Muenster has experienced annual totals between 229 and 639mm in its over 70 years of record; these values are typical of most other places in Saskatchewan.
An important feature of the climate of Saskatchewan is the frequent clear skies and the resulting sunny conditions. The province’s position in the lee of the Rocky Mountains and in the middle of the continent means that high surface pressure is frequently experienced. This high pressure in part explains the general aridity of the climate but also has other effects. One is the abundance of bright sunshine hours: many places in Saskatchewan have considerably more than 2,000 hours of bright sunshine each year, and Estevan, in the southeast, is known as the “sunniest place in Canada,” with an average of 2,435 hours of bright sunshine each year. The clear skies and general lack of humidity, along with frequently unmitigated winds, allow for large potential evapotranspiration (PET). This exacerbates the aridity and dictates that the climate can only support grasslands in the southern third of the province. In the north, where PET is lower, woody vegetation can grow. This is often a greater determinant of natural vegetation than the slight difference in total precipitation from north to south.