Too late for Autumn starts?

South Park’s greenhouse usually hands out garden starts to our food bank clients in September. (These have been chards, kales, winter lettuces and herbs to grow on a windowsill). This year, because of the heat & water challenges I’ve deferred beginning these until August 2. I know that I’ll need to have these as big as possible before the cold weather sets in (because after that time they really don’t grow until the onset of the warmer spring weather.) Your advise would be appreciated: how can I get them to grow quickly?