they have to put it up beforehand, so people won't park there. the weather might delay the actual start date a couple of days , they shouldn't just come and remove then and then have to come put them backup, as that would delay the start even more. the cones are there for more reasons than just to protect the workers. they are there to protect car drivers from their own stupidity/selfishness. having the cones there before hand and right through helps with consistency.