Do you need to winterize sprinklers in Las Vegas?
Las Vegas doesn't need a hard winterization blowout like colder climates do — but a handful of freezing nights each winter can still crack an exposed backflow preventer if it's not protected.
Las Vegas winters are mild, but not frost-free — the valley typically sees a handful of nights each winter that dip to or below freezing, usually in December and January. That's nowhere near the sustained freeze that makes a full compressed-air winterization blowout mandatory in colder states, but it's enough to crack an unprotected backflow preventer or exposed above-ground fitting on the wrong night.
What actually needs protection
The backflow preventer — required above grade by Nevada plumbing code — is the most exposed, most vulnerable part of the system, since it sits above ground year-round. An insulated cover (a simple foam or insulated box) over the backflow device before the first freeze watch of the season handles most of the real risk for a typical residential system.
When a full blowout makes sense anyway
If you're leaving the system off for an extended stretch over winter, or if a specific run of exposed above-ground pipe has frozen and cracked before, a proper compressed-air blowout of that section is worth doing. It's just not the valley-wide, every-household necessity it is somewhere that actually gets sustained hard freezes.
What to do if something did freeze and crack
If a hard freeze night catches an unprotected system and something cracks, don't just run it and 'see what happens' when temperatures warm up — running pressurized water through a cracked backflow device or fitting can make the damage and the mess worse. Have it inspected before you turn the system back on.