In northern climates where the ice-over routinely reaches a foot or more in thickness, ice fishing is a common winter pastime.

But in southwestern Pennsylvania, where roller-coaster winter temperatures can plunge below zero and spike into the 50s within a week, ice fishing fans sometimes skip entire seasons because of risky ice, and beginners can be justifiably skeptical of the whole thing.

As with all outdoors activities, common sense prevails. Plan for the worst and enjoy the best:

• Tell. Don't ice fish alone, and before you leave home, let someone know where you'll be and when you expect to return.

• Ice. A thickness of 4 inches of solid ice -- not 3 inches and some frozen slush -- is considered suitable to support one person and gear. Remember that ice thickness can fluctuate. Don't fish over springs, tributary water or moving water, or near exposed structure. If you're not absolutely sure, bore test holes on your way out onto the ice. For groups of people, don't trust ice under 7 inches.

• Snow. Covered skim-ice areas and obscured holes that were previously bored are especially dangerous. Remember that ice covering old holes will not be as thick as the rest of the surface, and that holes generally weaken the surrounding ice. Keep new holes at least 6 feet apart.

• Picks. Keep a pair of small ice picks connected by elastic cord slung over your shoulders and easily accessible. Homemade picks are OK, too. In an emergency, drive the picks into the ice and kick hard to push and pull yourself back on the ice.

• Rope. And just in case, tie a long rope to a tree or other shoreline anchor and stretch it to the area where you're fishing. In an emergency, seconds will count.

• Fire. Wet and cold, you could succumb to hypothermia before you make it back to the car. Keep stick matches or a lighter, and paper and other tinder, in a watertight container (Ziploc bags will do). Remember that if you need fire, you'll need it quickly and desperately at a moment when your hands and fingers may not be working well. And don't forget to bring dry clothes.

The Pennsylvania Fish and Boat Commission has more about ice fishing safety at www.fishandboat.com/icesafe.pdf.