The relationship between long-term weather and yield of 11 horticultural crops and one field crop in Wisconsin was determined for a 55-year period (1950–2005). The relationships among weather parameters and yield in Wisconsin were also compared with associations between weather and yields in Ontario, Canada, from a previous study. The number of days in a growing season with maximum temperatures 30 °C or greater (hot days) was negatively correlated with yields of beet for canning (r 2 = 0.15), green pea (r 2 = 0.16), onion (r2 = 0.08), and sweet corn for processing (r2 = 0.16) in Wisconsin. Hot days were also negatively correlated with yield of green pea (r2 = 0.16) in Ontario, Canada. Growing season precipitation in Wisconsin was positively correlated with yields of beet for canning (r2 = 0.18) and green pea (r2 = 0.09). An increase in yields of beet for canning in Wisconsin and green pea from Ontario was also observed with an increase in number of days with rainfall during the growing season (r2 = 0.12 and 0.15, respectively). Monthly minimum and maximum temperatures and hot days had an effect on vegetable yields in Wisconsin. A high number of days with precipitation in May and July was associated with yields of most vegetables and grain corn in Wisconsin. These results indicated the importance of the total and frequency of seasonal precipitation and the negative effect of exposure of crops to extreme temperatures on yields of vegetable crops.