If incomes for employed people are rising when unemployment is growing, they may be rising sufficiently that total income divided by the size entire labor force still goes up. But more precisely, note that the data set describes median income. Due to the high degree of collinearity between INC and the other variables, the coefficient on INC is not very reliable. The point estimates in Regression B2 suggest that the price effect is slightly smaller in absolute value during the summer. The unemployment rate has a negative effect in summer as opposed to a positive effect in winter.
Higher income has a larger negative effect in summer months than in the winter.
However, all of the slope-shifting dummy variable interaction terms have individually statistically insignificant parameter estimates. The straight summer dummy variable is no longer statistically significant either. There may have been no summer rainfall at all. If so, this interaction term would always have been zero. As it is, the interaction terms would be essentially a dummy variable for that one month, which isn't too informative.