The above climate weather data chart for London, Ontario Canada shows average monthly weather statistics with historic daily extremes. Weather climate statistics include monthly averages, maximum and minimum average mean temperatures, mean rainfall, mean snowfall & daily high and low extremes for temperature.
There are many ways to calculate "climate normals"; the most useful ones adhere to accepted standards. The WMO considers thirty years long enough to eliminate year-to-year variations.
Snow cover is the depth of snow on the ground, which is measured at several different points of the immediate area which is then averaged.
Normals for some of the statistics are taken from less than 30 years of records. The minimum number of years are defined by a "code" in the far right hand column. The Code Legend is shown below:
* "A": No more than 3 consecutive or 5 total missing years between 1971 to 2000.
* "B": At least 25 years of record between 1971 and 2000.
* "C": At least 20 years of record between 1971 and 2000.
* "D": At least 15 years of record between 1971 and 2000.