That is most likely the Back Flow Prevention for your sprinklers. There should be a valve that you can shut off on the BFP to stop the flow of water. Have it fixed before you need the sprinklers - which in this case may be Saturday. Back Flow Preventer
Yup! I had the sprinkler system back flow preventer freeze off they blow when it thawed, the 1st year in this house. I learned real quick how to turn the water supply to it off, and drain all the system lines. And now I do it early when the temps are reasonable and well before the 1st freeze. Yes, live and learn ... and I learned real well after the first time of a really bad experience.
Our first home here, a pipe burst inside, OVER THE BATHTUB! What luck! No subsequent damage. The plumber taught us every thing we need to know! We are quick learners knowing what we had avoided first hand.
Houses built in moderate warm climates arent built with freezing temps in mind. My house in Nebraska was much sturdier. The Windows had double panes and insulation was much better. We HAVE to prepare here.
Some folks are just not motivated to avoid disaster. Lol
PLUS, many of those colder locations have basements! There is where most of the plumbing is, inside where it's much warmer and protected. We have this crappy soil here and can't have basements. But they are nice to have.