Pennsylvania has always been the place to go for winter trout fishing. With the recent extension of the season on all of the state's streams and lakes through February, the waters open to frosty-fingered anglers have been broadened even further.

A coldwater species, trout tend to bite rather well at this time of year, in spite of ice-making air temperatures and stream readings not much above that. But their metabolisms are pumping at a slower pace, and it's wise to keep this in mind when drifting a nightcrawler into an emerald lair, jiggling a nymph past a sighted rooter or bobbing minnows on a frigid lake. Give them time to take, and make sure the lure, fly or bait is moving easily enough that they can catch it at their slowed-down winter speed.

To have the presence of mind and warmth of fingers to deliver your offering deftly and temptingly to a lethargic winter trout, think first of your own thermal needs: There's nothing surer to cause hasty deliveries, cursory coverage of the water and a general rushed attitude than frozen feet and stiff fingers.

Dressing warmly enough to be comfortable for winter fishing trips, it seems, is something we all must learn from experience -- say, freezing to the bones on eight or ten trips -- no matter how often experienced outdoorsmen tell us we ought to dress more warmly than we think necessary. Cotton next to the skin, wool over that, down on top of it all makes a good barrier against the cold. Steaming-hot soup, chocolate or coffee warms both the spirit and the body when you're about to turn into an ice cube.

Some serious anglers will have nothing to do with gloves, no matter how numb their fingers might get, considering them a hindrance to good contact with line and reel. A compromise solution for those with similar scruples is to buy a pair of $3 surgical gloves, available at most drugstores. These are then and tight-fitting enough that you can tie knots while wearing them, yet they do provide a modicum of warmth.

If your fingers still go numb and tingly, try this trick an Icelandic cross-country skier taught me: Put down your rod and swing both arms around as if you were pitching a softball or doing the backstroke.Do this rapidly for a minute or two. Centrifugal force will draw the blood down into your fingers and warm them quickly.

Choosing the right tackle is also vital; winter trout's metabolisms may be slowed by cold water, but their wariness and cautious outlook on life don't sleep. If anything, the trout are more line-shy and skittish than during summer, because the heightened clarity of the streams and the sparse shoreline surroundings help them see a clumsy human predator lumbering up to the water.

For spinning, hone down to two-pound line. If you find yourself breaking off with this fine, thread-like mono too often, go to four-pound, but never higher. Fly fishermen should consider 5X their thickest tippet choice for most situations; 6X and 7X will draw even more takes.

On most waters with standard regulations, bait is unquestionably the most potent offering for winter trout. Some ripe fish have been dropping eggs in recent months, whether successful in their spawning attempts or not, and most trout are more than willing to gobble up a choice salmon egg drifted on a gossamer line.

Use a short-shank, gold-plated hook in size No. 8 or 10, and impale a single egg on it. Add a tiny split shot a foot above that and drift the offering into deep, slow pools, eddies at the foot of rapids, and undercut banks where the current smoothes out. Worms will also take trout when fished in this manner, as will ice-fishing baits such as mousies, meal worms and corn borers. A small, frisky minnow does wonders on trout a foot or longer. In lakes that aren't yet frozen, try drifting with the same baits hanging close to the bottom near points, dropoffs and feeder creeks.

Not surprisingly, much of the limited diet of trout in streams during winter consists of immature aquatic insects. Consequently, fly fishermen who probe Pennsylvania's streams at this time of year do best with nymphs. Weighted mayfly and stonefly patterns drifted slowly through the deep pools and runs draw delicate, pecking strikes. But once they feel the string of steel, such finicky feeders can often turn out to be surprisingly frisky. Watch for the barest hesitation or upsteam movement of the fly line that could signal a gentle take from a not-so-gentle fish.

On the limestone streams, trout fishing is particularly good during winter because the creeks pour out from underground springs and run at a virtual year-round temperature in the 50 degrees range. They're quite fertile, as well, with much of the winter fare consisting of sow bugs, shrimp and scuds. Trout will actually move up into the beds of elodea and cress, shudder their bodies to knock loose the small crustaceans, then calmly swim back downstream and gobble up the free-drifting morsels they have rooted out. Look for such active feeders on Falling Spring, the Letort and Big Spring Creek. Time your cast so the imitation scud or shrimp floats over the fish after it has rooted in the weeds and is stationed back down below sipping in the fruits of its labor.

As of January 1, new 1980 fishing licenses ($14 for non-residents) are required in Pennsylvania. Seven-day permits ($9) are available at most sporting goods stores. The "Summary of Fishing Regulations and Laws" given out with your license lists all approved trout waters in the state by county. Many within Adams, Franklin and Cumberland counties are within reach for day trips.