Most traditional running shoes have mesh uppers and are meant to be ventilated. Otherwise sweat builds up inside the shoes, which is at best uncomfortable and can also encourage the development of athlete's foot. Because of the mesh, Scotchgard can't really waterproof them. Even if you waterproof the mesh, water will easily get in through the holes. I'm not as familiar with trail running shoes; I think they also have mesh uppers; perhaps others can offer info on them.

There are a number of good trail running shoes that have Gore-Tex liners. They'll keep your feet dry in conditions short of a stream crossing. The only downside is that they don't breathe quite as well as the lighter-weight mesh-upper shoes and they can be hot in the summer. My feet are frequently wet when I run from rain, snow, water crossing, etc., and I've found that since I started wearing injinji tetra socks (the ones with the seperate toe compartments) I haven't had any issues with blisters. My mesh-topped trail shoes drain better than my Gore-Tex ones too.

I've Scotchguarded all my running shoes for years and IMHO, has never negatively impacted breathability. Scotchguard does not waterproof them (which would keep them from breathing), it makes them water resistant. Same difference as in a watch... one you can swim in and the other you can only get wet in the shower/under the faucet.

Light dew and even a light rain is rebuffed by Scotchguard yet if I run in heavy rain or through a lot of tall, wet grass it will wick through.

If nothing else, SG one shoe and not the other. Then run through your wet field for comparison. Remember, it takes SG 24 hours to dry so plan accordingly. I usually spray a heavy coat on mine. 2 or3 passes. SG washes off in one washing so if you think you're losing breathability, it's easily resolved.

.. and like the other caller says, if they get dirty, you can wash them and they look like new. Just remember to SG them all over again.

Fergs

One possibility is wool running socks.  Wool retains its insulating ability when wet.

Len

Len: do you know of any brands that make wool running socks?

Running socks are like running shoes in my experience; manufacturers

make them only for the summer when you want breathability.  I 've

never seen thick running socks.

And Fergs:  it's definitlely not a lacing problem as my feet are fine until the temperature drops into the 20s.  And starting out warm doesn't help with running shoes, which are the inverse of boots.  Boots are meant to keep the outside air out and the inside air in.  Every running shoe I've seen is meant to let the inside air out and the outside air in (i.e. "breathability").  Hence the problem when the outside air is subfreezing.  Imagine trying to heat a cabin with a screen door in the winter.  Doesn't work.

Everyone's right on Scotch Guard not waterproofing.  I've found that the Brooks ASR (trail version of the Addrenaline) is a nice winter shoe as it doesn't have a mesh upper and is intended to function both on & off trail.  The lugs aren't super deep, but do a nice job of shedding snow.  If the shoe works for you, it's a good option.  Otherwise, you may want to ask your local running store about shoes for the winter.  I believe Nike makes a model too.

I can sympathize with you on the cold feet issue.  I run in Illinois and Michigan a lot during the winter and have learned to accept that my feet will forever be cold.  This is due partially to the fact that I am tall (6'5") with low body fat and low blood pressure.

As Len mentioned, Smartwool seems to be the best known brand for wool socks.  I haven't used them, but have never heard a bad thing about the brand.  You may want to just Google "wool running socks" as there are other brands and models made from wool. 

Recently, Drymax has come out with a cold weather running sock that appears to do a very nice job.  I did a test run in them and found the material to be comfortable as well as warm.  They only come in a heathered red color and are crew length, but its function over fashion in this case.  My only problem:  I wear a size 14 shoe and the XL was just a tad tight in the toe.  Drymax makes a XXL sizing, but not in this model sock (at present).

If you check www.Zombierunner.com, they carry the full line of Drymax socks as well as injinji and others.  It's at least a good place to start.

One other suggestion:  If the socks don't make a difference, try a single-use hand warmer pack in your shoe.  They're thin and may help keep your feet warm.  If you try it, I'd suggest using it on a short run first to make sure you're not blistering.

Good luck!