My lab loves to run through the brush and small streams so it's not just his feet that get cold and wet. I usually have to dry him off from top to bottom with a towel when we get home. I'm sure you can relate with your lab.
It's Tessa's most redeeming quality. After having a poodle mix, I love the wipe and go of a lab
We've got plenty of snow here. Normally winter only dumps a total of 3-5 feet of snow total here, though recently it's been more and much heavier.
If there is a lot of snow build up on your trails, you could always try boots like this
Ruffwear Polar Trexâ„¢ Winter Dog Boots - Tess has a set for the coulee trails around here and she loves them (only pair she hasn't managed out of yet), though I highly recommend the socks that go underneath as they can rub the fur/pads. They really help with all the brambles and tumbleweeds (yes, just like the westerns) that they get into, water - not so much.
I would suggest to minimize the cold water, like lakes and puddles, simply because they will get colder quicker. Make sure you watch for any signs of hypothermia and pack a back pack with emergency stuff just in case.
A good judge is if your cold, they're chilly, if your freezing, they're probably getting cold. Never go out any longer than YOU can handle, watch the dog at all times to judge their tolerance, and if you think you should turn around, do. Labs never know their own tolerances and are so willing to work/play that they could be going into shock and still go to fetch that dang ball. Gotta love'em.