I would think that once it is up, if you throw a cover over it, you will smother it.

How cold is cold? Clover is fairly cold tolerant.

If it is a temporary cold spell, you could throw clear plastic over the clover to hold the ground heat in and keep the frost off the plants. I wouldn't leave it on too long.

Fall sown grasses are mostly growing roots and then coming on in the spring. It may be the same with clover. The tops freeze and the roots give you a plant in the spring.

Thanks for the tips. I have way too much area of it sowed to place plastic on it.Its suppose to be in the 20's three nights in a row starting Thanksgiving night into Friday. Again the seed is sprouting or has already sprouted. It sounds like its suppose to be in the 40's and 50's for day time temps. Most nights in the middle to upper 30's over the next ten days. So it sounds like one really cold night then another 10 days of mid to average temps. I hope some of get enough of a start to get going next year. Thank so much.

As a new seedling with just the cotyledons showing, it may be susceptible to frost in the mid to low 20's.

I wouldn't try to really mulch it as you'll pretty much bury the seedlings although if the ground is bare, a very light dusting of fine mulch wouldn't hurt. You just don't want to cut them off from light.

Generally you would need at least several weeks of frost free weather from emergence until you have a couple sets of true leaves for the plants to survive the winter. However, you have a warmer and probably moister climate than mine, which would help with winter survival.

If it does freeze down and kill, you'll probably have more seed that didn't germinate yet, or you could re-seed once the ground is too cold to germinate so that it doesn't come up until spring.