According to the requirement for major field-crops' growth and development on weather and climate conditions in Canada,principles of agricultural meteorology and climatology,as well as impacts and trends of global climate change on the crop production,six key agrometeorological factors(extreme air temperature,heavy precipitation,strong wind,freezing,extreme soil moisture and effective heat-energy conditions for crop production) were selected for development and evaluation of twelve critical agrometeorological indicators(cool spell and heat wave days,maximal daily and ten-day precipitations,maximal daily wind speed,strong wind days,frost-free and freezing days,standardized precipitation index,seasonal water deficit,effective growing degree days and crop cumulative heat units).They can be used for scientific regionalization and rational development of different types of field crops,including warm season crops and cool season crops of annual herbaceous species,and over-wintering crops of biennial and perennial herbaceous and woody species in various agricultural regions across the country.This study is also based on plant growth and development requirements for cardinal temperatures and water conditions for three types of major field crops and actual weather and climate characteristics during crop growing and overwintering seasons in any agricultural years to determine growing season starting and ending days of various field crops in Canada.The results can be used for rational arrangement,optimal selection and proper plantation of suitable field crops in various agricultural regions of the country,efficient farm operation and management,science advice,policy development and decision-making,as well as similar scientific researches in other countries and regions in the future.