Extent of available data.
The 30-year normal average November precipitation values were calculated for the period of 1981-2010 by the Minnesota Climatology Working Group at the State Climatology Office and the MN DNR Division of Ecological and Water Resources. The 30-year normal values are calculated at the beginning of every decade and summarized in a 10 km grid. Changes in precipitation levels, patterns and the time of year it falls can have significant impacts on erosion, groundwater recharge, surface water flow, and vegetation type and growth rates. Because precipitation drives and limits many physical and biological processes, it is important to have these data to serve as a foundation for comparison to current precipitation levels and for detecting trends.