Lunar Synodical Period and Widespread Precipitation.
Precipitation activity over broad areas appears to be closely associated with the monthly lunisolar cycle. Indexes of precipitation in the continental United States over a continuous 50-year period, and 91-year daily histories of individual stations, reveal that heavy rains occur most frequently in the first and third weeks of the synodical month.
Bradley
D A
DA
Woodbury
M A
MA
Brier
G W
GW