Climate

CLIMATE varies widely in BC for 2 principal reasons: the diverse topography and the proximity to the Pacific Ocean. The main elements of climate—precipitation and temperature—are affected by factors such as elevation, latitude, air flow and particularly whether a location is coastal or inland. Generally speaking, moist Pacific air affects coastal regions by making them cooler in summer and warmer in winter than Interior regions, which are subject to what are called continental influences. Coastal regions enjoy the longest frost-free periods in Canada: up to 280 days a year in some years and in some southern areas. Average winter temperatures on the coast remain above 0°C and are the mildest in Canada, while average summer temperatures are 18°C or less. Coastal winters are cloudy and wet as a result of Pacific air masses dumping their load of moisture as they rise over the COAST MTS. Even so, there is wide variation within the region. VICTORIA, which is subject to more wind coming up the STRAIT OF JUAN DE FUCA, averages only 619 mm of precipitation annually, while VANCOUVER receives 1,113 mm, and OCEAN FALLS, the wettest populated place in the country, gets 4,386 mm. The absolute wettest spot in N America is HENDERSON LK on the southwest coast of VANCOUVER ISLAND, in from BARKELY SOUND. Despite the coast's reputation as "the Wet Coast," Vancouver is just the sixth wettest major city in Canada and Victoria receives 2,100 hours of sunshine per year, as much as any place in the southern prairies. Most of the precipitation falls as rain. The coast, especially in the south, gets very little snow; in fact, annual averages are the lowest in southern Canada. According to Environment Canada's Climate Severity Index, the South Coast has the best climate in Canada in terms of human comfort and well-being.

The Interior of the province has a completely different climate; it is much drier and, since it is not modified by the fairly constant temperature of the Pacific, is subject to greater temperature extremes. Summers are hot, particularly in the south, where LYTTON, OLIVER and OSOYOOS are often the hot spots in the country, reaching temperatures well in excess of 30°C. Winters, on the other hand, are much colder than on the coast, though the cold is broken by periodic mild Pacific storms that work their way through the mountains. The western part of the southern Interior is the driest part of the province because it is in the rainshadow of the CASCADE MTS. The OKANAGAN VALLEY, for example, receives a mere 250 mm of precipitation annually. Much of the eastern part of the southern Interior lies in what is called the Interior Wet Belt and receives considerably more precipitation. This occurs because warm, dry air over the Okanagan, for instance, picks up moisture as it passes over the large LAKES of the southern Interior and drops it again as it hits the CARIBOO, MONASHEE, and SELKIRK mountains on the west side of the ROCKY MT TRENCH. The central and northern Interior are also wet (PRINCE GEORGE receives 628 mm of precipitation), colder in the winter and not as hot in the summer. Annual snowfall ranges from 50 to 100 cm in the dry valleys of the south to 400 cm around REVELSTOKE and in the north. The northeast corner of the province has its own climate, which is an extension of the continental prairie climate. It is colder in winter than the rest of the north (but enjoys considerably more winter sunshine than coastal areas) and it enjoys warm summer temperatures and an extended frost-free period that allows AGRICULTURE to flourish.

Despite the general trends described, BC's climate is characterized by many local anomalies that defy generalization. The "pocket desert" near Osoyoos, a northern extension of the Great Basin, is one of these. TELEGRAPH CREEK on the middle STIKINE R in the northwest of the province, has much drier weather than the rest of the river corridor and is hot enough in the summer to support many fruits and vegetable crops that don't grow well in the northwest generally. Another is the GULF ISLANDS, which despite their coastal location, enjoy a comparatively drier Mediterranean-like climate because they lie in the rainshadow of the mountains on Vancouver Island and the Olympic Peninsula.