Zone 3 -40 to – 30 degrees F (-40 to -34 degrees C)
Long cold winters are the foremost characteristic of this climatic zone which forms an arc of varying width around the Northern Hemisphere. In North America, from as far north as Point Hope on the Arctic Ocean in Alaska, well above the Arctic Circle, this zone swings south to the center of the continent. Here it straddles the Canadian/US border and dips as far south as a few isolated mountain ranges in Colorado and New Mexico in the mid 30s latitude. The zone then rises northward again as it approaches the Atlantic Ocean and eventually reaches Ungava Bay in northern Quebec, Zone 3 forms a similar arc in Eurasia and due largely to the influence of the Gulf Stream, it extends far into northern Scandinavia than would perhaps be expected. As the distance from the ocean increases, winter temperatures become colder and summer temperatures become warmer. In climatic terms, this effect is known as continentality, and it plays a major role in shaping the climate of these large continents and explains why Zone 3 reaches so far south into both these landmasses.
Zone 3 is a typical continental climate and the average annual lowest temperature ranges between -40 to -30 degrees F (-40 to -34 degrees C), while the average summer highs can range between 86 to 100 degrees F (30 to 38 degrees C). This climate evokes images of blizzards and frostbite, blowing snow and whiteouts, but this tells only half the story. It is actually a place with dramatically different seasons. Summer can be quite pleasant and often the majority of the precipitation falls at this time during thunderstorms, promoting a rich growing season. Spring and fall are typically short and often variable. Often, one week in either of these seasons can experience extreme temperature swings. The growing season (frost-free days) varies from under 60 days to more than 120 days. Percipitation in Zone 3 varies. Mountainous regions of British Columbia can experiences above 80 in (200cm) of rainfall per year whereas the driest areas of the prairies receive well under 20in (50cm). The amount roughly determines the type of flora present in an area. In very general terms, areas that receive over 25 in (62 cm)annually are forested; those with less are grassland.