Simple 2D Parallel Heat Conduction
 

I am running a simple 2D heat condition problem in parallel. The domain is decomposed into 4 equal regions in the horizontal direction. The temperature contour looks like file 4 in attachment. However, While when I am running the case on 1 processor the contour looks like file 1. As you see, the temperatures do not seem to be right at the intersection of the domains, solved by different processors. Any idea what is wrong?