Can you apply 2-4 D Ester Herbicide in cool weather?

I just sprayed 2-4 D for the first time on my lawn to get rid of wild onions. My local Co-Op, which supplied the 2-4 D, advised me that it should be used in temperatures below 80 degrees. I don't think I would spray below 50 degrees however. It is my understanding that spraying above 80 degrees would burn up everything it touched.