If you see weeds then I would say no. Can you spot treat for now? It would save money and you wouldn't be putting down as much chemical.
Good lawn has few weeds because the turf is so thick that it chokes out weeds. Channel your efforts into fertilizer. Keep the turf mowed a little higher. It helps drown the weeds and conserves water.
I live in N.W. Alabama. About two weeks ago, I sprayed my entire property with 2.5 oz of Weed-B-Gone to each gallon of water. Weeds were activaly grownig and some blooming. Temperature was within two degrees of what was recommended. NO KILL WHATSOEVER!
I think the formula may have changed because I have sprayed this product over the last 15 years and under similar conditions with good results.
I will spray later and be sure it not too early.