The only years weve had test weight issues is when the corn has been slow to mature...... Conditions like last year, we had very little rain, and no heat all summer, somehow made for good yeild, but poor test weight.   1993 was heavy rainfall year here, corn didn't mature.    Yield, test weight, and moisture was all messed up.   Have never had a test weight issue because of heat........but it doesnt get very hot for long periods of time here either.