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The productivity of a dry mixed prairie site at Onefour, AB Canada was sampled annually from 1930 through 2014, with only 5 years missing. Simple weather records were collected concurrently. In addition to updating previous modeling of weather effects on productivity, changes over time were examined to test for climate change. Over the 80 years, forage productivity increased with time (linear R2 = 0.335; quadratic R2 = 0.439). To refine the effect of time more clearly, we applied a linear plateau model to productivity which revealed a break point in 1973, after which there was a linear increase in productivity. Post 1973, the climate became more humid with a linear increase in April-July precipitation (r = 0.30) and a linear decrease in May-July pan evaporation (r = -0.58). There was little change in maximum daily temperature (r = -0.04). Stepwise multiple regression relating weather factors to productivity were separately for the two 40 year periods. In the first 40 years precipitation was the main explanatory variable followed by maximum temperature (multiple R2=0.64). This was similar to previous modeling efforts. In the second 40 years pan evaporation was the main explanatory variable followed by precipitation (multiple R2=0.57). As these two variables changed with time, climate change was partly driving yearly variations in productivity during the second 40 years.