The data sets
corn.yield
and
corn.rain
give the corn yields and rainfall measurements in six U.S. states, for the years 1890-1927.
Ezekiel, M. and Fox, K.A. (1959). Methods of Correlation and Regression Analysis. New York: John Wiley and Sons, Inc.
Data originally from Misner, E.G. (1928). Studies of the Relationship of Weather to the Production and Price of Farm Products, I. Corn. Mimeographed publication, Cornell University.