The researchers, who represent five institutions from the United States and Great Britain, offered several reasons why sunspot peaks may affect rainfall. The increased solar energy associated with sunspots, they suggest, heats both land and sea, forcing moist air to rise and triggering precipitation. It may also induce El Nio events, which increase rainfall in East Africa.

While sunspot peaks augur extraordinarily wet rainy seasons, heavy rains are possible at other times as well, Stager acknowledged. But most of the rainiest times, he said, are consistently coupled with the predictable rhythms of sunspot peaks.

"When you think of climate troubles in Africa, it's usually about drought," Stager said. "You don't often think of the opposite situation.

"Too much rain can create just as many problems."