Sounds as if the onions have bolted. Pull a couple up and see if there is a decent size onion at the bottom. A lot of veggie crops have been stressed this year by the heat in spring, the drought and the cool weather in June early July. Not a lot you can do really just try again next year and keep your veg. plants watered if it is hot and dry.

thanks moon growe

The bees may enjoy the onion flowers so leave a few for them, at least something will enjoy the onions!

Don't give up growing veg though - this has been a bad year. Better luck to us all next year!