I suppose you need to know which weeds germinate when. I got some weeds already and my spinach has put in an appearance but the first carrots and lettuce are up. I also have a few weed brassicas so presume I can get started with those as well.
I do think perhaps the thermometer takes the guess work out of it. Never seen anyone trying the bum method!!
It is interesting about the daily fluctuations for celery. Some of the optimums seem surprisingly high. I suppose on a sunny day the temperatures suddenly shoot up.
The listing does rather reinforce my sowing practice, spinach outside, squashes on the radiator, beans on the windowsill etc.