Simulated difference in the mean annual number of days with a minimum temperature less than 10F (Tmin < 10F) for the Midwest region, for the 2041-2070 time period with respect to the reference period of 1980-2000 (top). Color with hatching (category 3) indicates that more than 50% of the models show a statistically significant change in the number of days, and more than 67% agree on the sign of the change (see text). Mean annual number of days with Tmin < 10F for the 1980-2000 reference period (bottom left). Simulated mean annual number of days with Tmin < 10F for the 2041-2070 future time period (bottom right). These are multi-model means from 8 NARCCAP regional climate simulations for the high (A2) emissions scenario. Grid boxes whose centers are over the Great Lakes or outside the 8-state region are masked out. Changes are downward everywhere. Decreases are largest in the north and become smaller southward, in a pattern similar to the present-day climatology.