All you have to do is drive Seward Highway south of Anchorage to see why early-season backcountry skaters need to know where they stand.
At Potter Marsh, skaters explore the frozen marshland. Some cut turns, others play pick-up hockey. About 40 miles south at Portage Lake, water in the 600-foot-deep lake remains liquid.
"Nothing but open water," said Lezlie Murray, director of the U.S. Forest Service's Begich, Boggs Visitor Center in Portage, Tuesday morning as she looked at a Web cam focused on the lake. "It isn't frozen yet. I can still see the wave action.
"The thing that's hard to comprehend is that Portage Lake is 600-800 feet deep in its deepest spots. It takes a very good freeze."
And therein lies the dilemma for those trying to make sense of sub-zero temperatures after a particularly warm autumn. There's ice out there, but what's safe?
This week's face-slap of frigid weather is certainly making more areas skater-friendly, but it hasn't solidified everything completely. Tuesday morning dawned at minus-31 in Willow, minus-25 in the Eagle River valley and minus-17 on the east side of Anchorage, according to the National Weather Service.
That about-face followed a sweltering October that averaged 6 degrees higher than normal, with the temperature dipping below freezing only 10 of the 31 days.
"We're paying for it in November," said Todd Foisy, a meteorologist at the National Weather Service office in Anchorage.
Neither Westchester Lagoon nor Goose Lake, two of Anchorage's most popular skating venues, are ready for skaters. Both are unplowed.
John McCleary, recreation superintendent for Anchorage Parks and Recreation Department, said several city lakes were tested Saturday. Jewel Lake had 6 inches of ice, while the other Anchorage lakes were at 4 inches. Eagle River lakes averaged 7 inches.
"There's no doubt it would be thicker now," he said, noting the sub-zero temperatures over the last few days.
McCleary cautioned that measurements are taken at one spot, and such things as unmarked springs can make ice much thinner in other areas.
Once a depth of 10 inches is reached, hot mopping using a light truck can begin at places like Westchester Lagoon. At 12 inches, the municipality's 300-gallon trucks for hot mopping can take to the ice.
Some skaters drill to test ice thickness themselves. But most importantly, they should plan for safety.
• Skate with a partner.
• Carry a throw bag with a life line. And take ice claws for climbing out of open water onto solid ice.
The Web site www.nordicskater, a Vermont business that caters to long-distance and outdoor skaters, sells commercially made ice claws online for $15-$20. Do-it-yourselfers can make their own.
Simply drive a sturdy nail into the end of a one-inch or larger dowel the length of your hand, and then use a file or grinder to sharpen the exposed end of the nail to a point. All you need here is a sharp, pointed tool you can drive in the ice. You want two of them.
Their use is simple. If you fall through the ice, you drive these devices into nearby firm ice to pull yourself out. The best way to carry ice claws is to drill a hole in each one to accommodate the pointy end of the other. Push the claws together this way end to end, so the points are safely covered, and then hang them around your neck on a string.
That way they'll be handy if you ever need them, which hopefully you won't.
Still, ice claws are a good idea for anyone traveling on ice --whether walking, snowshoeing, skiing, skating or skate skiing.
Reach reporter Mike Campbell at firstname.lastname@example.org or 257-4329.
Precautions on ice
Snowmachiners should keep a dry set of clothes in a watertight vacuum bag. Put your cell phone in a sealable plastic bag.
If you fall in, turn where you came from -- that ice is probably strongest. Put your hands and arms on the unbroken surface. This is where a pair of nails, sharpened screwdrivers or ice picks come in handy in providing the extra traction you need to pull yourself up onto the ice.
Kick your feet and dig in your ice picks -- if you have them -- to work your way back onto the solid ice. If your clothes have trapped a lot of water, you may have to lift yourself partially out of the water on your elbows to let the water drain before starting forward.
Lie flat on the ice once you are out and roll away from the hole to keep your weight spread out. This may help prevent you from breaking through again.
Get to a warm, dry, sheltered area and re-warm yourself immediately.