Warping ply

The weather's getting nice & toasty here, 29 (C) today,
& I'm cutting up some 12mm pine ply for a project,
however by the time I get to gluing up, it has warped enough to make the process a pita.

Anyone have any tips on how to deal with this prob?
 
You can spray some water on the concave side to add some moisture that has been lost.

After cutting I stand the pieces vertical so the sides dry evenly as much as possible but assemble soon after cutting (within 4 hours).

Yes it is a PITA.