Sunspot numbers and area-weighted united states monthly temperature and precipitation

Spectral analyses were made of derived area-index series of areas subject to extreme temperatures and precipitation as well as cross-spectral analyses of the area-index series with double sunspot cycle (Zurich) numbers. Superposed epoch analyses also were made of area-index series versus various double-sunspot cycle phases. Area series for wet and dry Junes, warm Junes, defined June drought, and warm Januaries all show statistically significant double sunspot cycle (21 year) periodicities. The 21-year cycle of above-normal June precipitation is most striking and has not received previous recognition.Journal Paper No. J-10007 of the Iowa Agric. and Home Econ. Exp. Stn., Iowa State University, Ames, IA, 50011, Project 2397.