British Columbia has a huge variation in climate from desert to rainforest. Due to BC's complex physiography, it is no surprise that precipitation pattern can vary dramatically in a small spatial scale. Precipitation is influence by factors such as elevation, aspect, distance from the coast and valley system. As elevation increase orographic uplift of air parcel causes a drop in temperature and the ability to hold moisture. The higher the elevation, precipitation will more likely occur. East and West facing aspect has a remarkable difference in precipitation in a local scale or a regional scale. The prevailing wind in the BC latitude is westerly therefore west facing slope will receive more precipitation since it is the windward side where air ascent orographically. East facing aspect will have much lower amount of precipitation because it lies on the leeward side where descent air causes a rainshadow effect. Further away from the coast, the moisture gradient decreases as continentality effect dominates. Lastly valley systems also need to be considered because valley bottom receive less precipitation. Air mass containing moisture may skip these valley system because of the height of the valley walls.