Sprinklers are needed based on weather requirements. If it is going to be warm, then its nice to have them for the weather. If we have a mild spring, then you can wait to activate them for the season.
You can always get them ready to run but turn the timer off. That way you are ready when the weather hits. We encourage this as it gets very busy for us when it gets warm out of the blue.
Typically, we start activating sprinklers in early-mid April.