cold weather auto trans question

the weather's been getting cold around here lately (down into the 30's at night) and i noticed in my truck when i start it at work and head out my transmission shifts perfectly fine thru all 5 gears but when it get's to the end of the shifting the torque converted doesn't lock up right away like it normally does in the summer, takes a few miles to do so, just wondered if they're all like this, i figured the fluid just needed a little time to warm up but i wasn't sure, i'm taking it in for a flush next month anyways and planned on doing so anyways, it did this same thing last year in the winter

 

ahhhh i figured it was something to do with that, thanks for the fast reply!

 

the funny thing about transmissions is i build them for a living and we are actually installing transmission fluid "warmers" but then it also has a cooler too hahahaha