Normal conditions

The World Meteorological Organization (WMO) established a standard for what normal is. The standard is daily data averaged over a 30-year period. At the beginning of each new decade (1980s, 1990s, 2000s etc...), this 30-year span is updated to include the most recent decade. The normals calculated during the 1990s were derived from the 30-year period of January 1, 1961 to January 1, 1991. For the 2000s, normals are calculated from the 30-year period of January 1, 1971 to January 1, 2001. The following is a short list of 30-year spans used to calculate normals through the latter half of the 20th century:

1960s = Jan. 01, 1941 - Jan. 01, 1971
1970s = Jan. 01, 1951 - Jan. 01, 1981
1980s = Jan. 01, 1961 - Jan. 01, 1991
1990s = Jan. 01, 1971 - Jan. 01, 2001
2000s = Jan. 01, 1981 - Jan. 01, 2011

Notice the pattern from the above representation of normals over recent history. Current normals are calculated from the 30-year span between Jan. 01, 1971 to Jan. 01, 2001.

normal Type

NOTE: The "Temperatures" link below opens in a new window.

Temperatures

Precipitation