Rainfall changes in summer caused by st. Louis.

Precipitation in and around St. Louis was investigated to study urban influences on summer precipitation conditions. Prerain winds were used to define the "downwind area" where influences would be greatest, and wind-sorted rains were combined into monthly and summer totals. Seventy-five percent of the 16 rain patterns revealed a rainfall maximization downwind of the city, and the rainfall in the downwind area was 22.7 percent more than the rainfall upwind of St. Louis where no urban influences existed. Various statistical tests of the summer rainfall distribution reveal the downwind rainfall to be significantly greater than elsewhere and supportive of other findings that St. Louis increases rainfall.