The right time to sow ones seed.....

So the time has come to take on the devils back garden again. Going for a mass attack to turn the soil where the turf once was. Took the turf up last year then the rains came and put a stop to everything. So tomorrow is all about putting turning the soil and removing weeds and larger stones followed by putting down the new top soil. Question is when am I best off putting the grass seed down?? With the weather as cold as it is if I put it down and water it tomorrow I worry if it gets cold then it will die off before it even gets going. What would you clever folk suggest??