When will the new precipitation “normals” be calculated?

Pricey Tom,
A number of of the current years have produced above-normal precipitation. When will these wet years be figured into a new “regular” for Chicago?
— Scott Williams,
Park Ridge
Pricey Scott,
Precipitation normals, and normals for all different meteorological variables akin to temperature and moisture content, are calculated (worldwide) as soon as every 10 years, using a 30-yr average.
The present normals are based mostly on 1981-2010. The subsequent recalculation will probably be achieved for 1991-2020.
A 30-yr interval has been chosen as the idea for determining normals for meteorological variables because it comes closest to giving an accurate reading of what the typical weather is at a location, whereas realizing that lengthy-range climate is probably present process modifications over time.

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