A dry-lot dairy, experienced two inches of rainfall in a span of two days posing challenges to corral and disease management. Within one week of the start of rain, the number of mastitis cases doubled in the hospital pen and there was a four-fold increase in systemically ill cows with mastitis. The most likely organism in this outbreak is Escherichia coli. Lipopolysaccharide, in the E. coli membrane triggers cell responses resulting in systemic production and release of pro-inflammatory mediators. The outbreak at the dairy was not solely a consequence of increased bacterial contamination of teat ends, but augmented by inadequate preventative and control measures against mastitis. Changes to the milking routine will improve mastitis detection, milk let down, and contact time for disinfectants, thus decreasing the likelihood of future outbreaks. Also, implementation of an on-farm culture program could decrease the cost and usage of antibiotics.