Depends on the seeds and the air and soil temperature.

what were you thinking of sowing TPV?
it will make a difference.

As a very general rule if weed seeds germinate then the soil has warmed up enough

Sorry Pam I don't buy that weeds seeds germinate long before the soil is ready to germinate freshly planted seed. The weed seeds sit there for years simply waiting for a window of opportunity.

Thanks to all going to start sowing