Drop down to 1\4 oz & use the same plastic as your Texas Rig.

I gave up using "jigs" after getting hung up about a dozen times without catching anything on them.  Instead, I texas-rig a crawdad bait (sometimes putting a skirt in front of it and sometimes not).  These are cheaper and, at the same time, a lot more weedless.  They are better for swimming than most other jigs, too.

If your still getting out in your neck of the woods, good on you!  I think I'm about done for the year here in WI since the snow is on the ground and sticking. 

 

Downsizing is a good idea, especially in cold temps.  Line watching is a must, and keeping a finger on the line is great too.  Oftentimes thats the only way I'll notice my jig being picked up.  Go as slow as you can, and then try to be slower.  Its tough, especially for those who enjoy moving baits like a crankbait or spinning bait. 

 

Muck bottoms are tough, and like Mark said, most lakes around the Northern Midwest have it.  Going heavier will let you feel the bottom but, you'll be pulling through that muck and getting hung up a lot.  As you develop a feel for where the fish are at you can become more picky about where you throw that jig. 

 

Take a look online to see if you can find lake maps with marked bottoms.  Over the winter is a great time to do this, find lakes with streches of rock, gravel, sand, all of which are much more enjoyable to fish a jig on than mucky weedy mess.

For that depth, I'd fish lighter jigs like Catt suggested.   Swim Jigs and Chatterbaits work well.  Don't be too upset about not getting them to work.  Like I said previously, I fish texas rigged brush hogs/sweet beavers where most people would fish jigs.  I just do better on them.  Weightless brushhogs around cover are ridiculous here. 

 

Weightless or Pegged weight, A T-Rig is completely weedless and nearly the same presentation as a jig.