The climate of the Great Plains varies greatly from north to south and from east to west. Southern areas of the region can have high temperatures for much of the year while northern parts are often far cooler. Eastern areas are also much wetter than the semi-arid west.
Temperatures in January and February are very low throughout the region, varying from 40 degrees Fahrenheit in the Southern Plains to 10 degrees Fahrenheit in the Canadian Prairies. Summer temperatures are much higher, averaging at around 80 degrees Fahrenheit across the Southern Plains and 66 degrees Fahrenheit in the Canadian Prairies.
Rainfall increases significantly from north-west to south-east, the south-east having over 40 inches per year compared to less than 14 inches in some parts of Canada and Montana. Spring in the Great Plains is characterized by thunderstorms with heavy rainfall, high winds and tornadoes. Snow is common in most of the Plains during winter, varying from 1 inch in the southern regions to over 40 inches in northern sections.
The varying climate of the plains is largely due to the movement of different air masses. Dry, cold masses from Canada bring cold, dry air across the Plains while northward moving air masses originating from the Gulf of Mexico and Caribbean often bring warm, moist air to the region. Furthermore, warm, dry air can move up from the south-western deserts and Pacific Ocean air often moves east, crossing mountain ranges that produces a significant warming and drying effect.