On my place I actually found a very few scattered oaks that had a few mature acorns.  I honestly thought all acorns had fallen off during the drought.  Now the amount of acorns I found is so low deer will scarf them up the instant they hit the ground, but it is interesting that a few made it through the drought.  And all of the trees I found with acorns were around the edges of food plots.  Probably due to the better soil and lack of competition with other trees for soil moisture.