Not To Be Fooled is correct in that in order to lower the backseats in Toyotas, each half section has a knob in the back of it on the top that you pull up to release the lock and it allows that section to move forward/down.
Other things I would recommend is (i) always keeping your ice scraper (hopefully you have a small one) in the driver's side door pocket and (ii) going to WalMart and purchasing Lock De-Icer manufactured by Victor? in the automobile section for less than $2 bec your vehicle locks (3) probably may contain moisture/condensation inside and could possibly freeze during the winter, thus preventing key insertion or turning etc until the temperature rises....
Hope the Above Info Helps!