In order to understand how current environmental conditions affect farmer decision making the levels of grass and soil condition are examined in the decision on when to turn cattle out from winter housing to spring grazing on Irish dairy farms. Five years of satellite derived Normalised Difference Vegetation Index MODIS data, as a proxy for grass growth data, were used along with daily rainfall data and turn out dates from 199 dairy farms. Using GIS analysis conditions at the time of turn out were determined at the date and location of the event. A panel analysis shows that farmers respond to early growth but not immediately, gaining three and half days extra grazing for every week that grass growth is early. The inertia in decision making around a preferred date was shown by using the previous year’s turn out date in the model. We can accurately predict when turn out occurs with a RMSE of 10 days, compared to average on farm range of dates over the 2008-2012 period of 25 days.