Take the plunge
Cold plunge pools were invented by Romans who probably figured out that immersing the body in 50- to 60-degree water stimulates circulation, relieves inflammation and detoxifies pores. The managers of today's most luxurious spas know this too, which is why Laguna Beach's Spa Montage ( 271-6953, www.spamontage.com) has a 57-degree cold plunge, Carlsbad's Spa at La Costa ( 854-5000, www.lacosta.com) has a cold plunge and an outdoor Roman waterfall, and Rancho Santa Fe's Spa at Rancho Valencia ( 548-3664, www.ranchovalencia.com) has three plunge pools, one of which is invigoratingly frigid. Use of the plunges and pools is included in the cost of spa treatments; at Spa La Costa, nonguests can pay $60 for day use, $30 for half-day.
Lounge in a vodka freezer
In scorching Vegas, head to Mandalay Bay's Imperial Russia-themed Red Square restaurant ( 632-7800, www.mandalaybay.com/dining). Just thinking of Siberia should cool you down -- but the real goose bumps come upon entering the exclusive glass-walled vodka vault, kept at minus 10 degrees (coats are available to borrow). If you noticed the big, headless statue of Lenin at the restaurant's entrance, you'll notice his head in here -- frozen in an ice block that doubles as a tasting table. For a more communal experience, sit at the 25-foot-long bar; its top is ice. Order one of the brain freeze-inducing cocktails (like the potent Chernobyl), but beware that prices here aren't for the proletariat. Minimum purchase is one bottle, which starts at $200, but only eight people can fit in the freezer. If you'd rather chill locally, Nic's in Beverly Hills ( 550-5707, www.nicsbeverlyhills.com) also has a walk-in vodka freezer, called the VodBox, where high-end tastings come with a vodka sommelier. Guests don faux fur coats to enter the room, which is kept at a biting 15 degrees. Minimum order: two tastes at $21 per person; three tastes is $30 per person.
Just ask: Qua?
Qua, Caesars Palace's immense spa () 782-0655, www.quabathsandspa.com), like Rome itself, puts forth myriad offerings. Foremost to heat evaders is the blue-hued Arctic Ice Room, where "snow" perpetually falls. Inhale the minty 55-degree air as you rub ice chips against your skin, an ancient European cleansing tradition. Next, immerse yourself in the coldest of the spa's three Roman baths, the Frigidarium. Last, visit the Crystal Body Art Room for a customized Swarovski skin design so that when you're back in the heat you'll still be glittering like winter. Use of the ice room is included in the cost of a treatment; otherwise, $45 per day to use the facilities.
Really plunge in
At the Punch Bowls, more formally known as Santa Paula Canyon Falls, you can leap off stories-high rocks into chilly water holes. When the adrenaline rush recedes, you can revel in the refreshing nippiness surrounding you. To get there, take the popular (but, in places, hard to follow) Last Chance Trail in Ventura County's portion of Los Padres National Forest (Ojai District,  646-4348). The trail begins at two points near the entrance to Thomas Aquinas College, meanders past an old oil well, through sycamore groves and deposits you at a narrow sandstone gorge about six miles later. Here, beautiful waterfalls cascade into deep pools, and this is where you dip -- or dive -- into a Punch Bowl. Total cost: leg power, gas and a $5 Adventure Pass. For a description of the hike, go to www.fs.fed.us/r5/lospadres/recreation/trails/ord/#paula.
Skip the niceties -- and the mammoth tab -- and strap on some skates. Lake Arrowhead has a particularly impressive rink, the Ice Castle ( 337-0802, www.icecastle.us). Its large, mirrored facility is home to accomplished staffers, including former Olympians and Michelle Kwan's onetime coach. There's at least one public session every day; cost is $10 including skates. In San Diego, Kroc Center Ice [(619) 269-1498, www.kroccenterice.com) also offers public skating at its NHL regulation-size rink nearly daily (check the website for exact times) and charges only $9 total for admission and skates ($6.50 on Wednesdays, when skate rental is free). Profits go toward upkeep of this surprisingly upscale Salvation Army facility, so no one will call you a cheapskate for paying less to come here.
Take the tram
Think Palm Springs, and you likely don't think "brrr." But take the Palm Springs Aerial Tramway up Mt. San Jacinto and you'll find an affordable, crisp place where it's always about 30 degrees cooler than the desert floor ( 515-8726, www.pstramway.com; $22 for adults, $14.95 for 3 to 12, younger than 3, free). This is the world's largest rotating tram car; it suspends riders 8,500 feet above Chino Canyon, then deposits them at Mountain Station, where they can enjoy the glacial temperature, watch a short film about the Tramway's history, have a cold drink at the Lookout Lounge or, depending on season, romp in the snow (OK, not in summer). Heartier souls can take a 5.5-mile hike to the mountain's even-chillier peak at 10, 834 feet.