We did a little survey and found that, in general, the higher-end the casino, the more likely it is to heat its pools. Among the dozen casinos we categorize as high end, including Bellagio, Caesars, Four Seasons, Green Valley Ranch, Hard Rock, Hyatt, Mirage, Paris, Palms, Rampart, Ritz-Carlton, and Venetian, only Green Valley Ranch doesn't have a heated pool.
Out of 32 mid-range casinos, 24 have heated pools. Those that do: Aladdin, Bally's, Excalibur, Flamingo, Golden Nugget, Imperial Palace, Las Vegas Hilton, Luxor, Mandalay Bay, MGM Grand, Monte Carlo, New Frontier, New York-New York, Orleans, Palace Station, Rio, Sam's Town, San Remo, Stratosphere, Suncoast, Sunset Station, Texas Station, Treasure Island, and Tuscany. Those that don't: Boulder Station, Circus Circus, Harrah's, Riviera, Sahara, Silverton, Stardust, Tropicana.
On the low end, three do (Gold Coast, Lady Luck, Westward Ho) and 11 don't (Boardwalk, Bourbon Street, California, Casino Royale, Fitzgeralds, Four Queens, Fremont, Las Vegas Club, Main Street Station, Plaza, and Terrible's).
