I would consider the easiest possible fix and that is to go to a shop that has the proper tools and have the transmission fluid level checked. You may have developed a small fluid leak that would not have caused any concern, but now with the "cold" weather the transmission fluid level being low will be more evident. A technician needs a scan tool and the proper filling nozzle to add fluid to this model transmission. This is assuming the Check engine light is not on, if it is it should be scanned for transmission fault codes.