its too cold for glyphosate. it can work but with those temps id say about 8 weeks for a 50 percent kill. the only herbicides you can really use to come back in ten days with seed are, hmmm , nothing really. residual products in the soil can affect seed germination rates. post emergent herbicides can have limited pre-emergent qualities.

wait till it warms up, spray it all with glyphosate, plant grass sod. u can still go with seed but dont expect perfect results

Roundup is the most recognized brand of Glyphosate used as non-selective herbicide. Read and follow the directions carefully. Vegetation to be killed has to be actively growing. Fertilize it first and then kill it. If you have temps in the 30's then it may be too cold for glyphosate to be effective. Is your grass actively growing ? Roundup is as commercial as it gets. It is used extensively in agriculture. You can plant grass seed 3 days after spraying roundup. I have seen roundup sprayed in the morning and rye planted in the afternoon of the same day.
Bill Hill

Why are you trying to kill the lawn now? Are you getting ready to reseed and replace the lawn? If so, I'm concerned that if you wait until the grass is growing enough to kill with glyphosate that you're going to have trouble getting it to establish well enough before the heat of summer kicks in. Late summer/early fall would be a better time for that kind of project.

bpgreen:

I may take your advice depending how much sod would cost me. where I live it is usually cold at night and early morning, even in the summer. Last summer I used my central air twice and only for a couple of hours in the evening. In fact, I had ice formed on Easter Sunday in an outside puddle.

All the good advice above is true. It's too cold and the weeds must be active for RU, but you do have an option, for even right now!!!!!

Northern Tool & Eqt has your weed killer - see link below. (don't laugh!)

Here is a link that might be useful: Weed Dragon