The lake was formed about 20,000 years ago when rising magma-encountered groundwater resulting in violent steam explosions. The resulting explosions formed a broad shallow crater, which later filled with water. North Twin has 112 surface acres, average depth of 40?, and a maximum depth of 60 feet. The pine forests that ring North Twin are open at the beach and boat ramp on the north shore. The lake harbors healthy numbers of stocked rainbow trout and illegally introduced bullhead. Fishing for rainbow trout here can be very good with an average catch is 8 to 12 inches in length.
Locals do well angling near the shorelines early and late in the day using bait, flies, or lures. The best bait fishing is along the west shore in the deeper holes using red eggs, power bait, or marshmallows and worms suspended just off the bottom. Rooster Tails, Panther Martins, and dark flies trolled slowly or cast toward shore catch many fish. Fly-fishing is most effective near shore as there are some good hatches of mayflies, caddis, damsels, and flying ants. A boat or float tube is best for fishing on the lake, due to the limited space for back casts.
Water levels fluctuate slightly during the year but not enough to affect fishing. The lake supports extensive weedbeds that are prime trout territory. The majority of shore fishing is done from the west shore where the drop-off is steepest. No motors are allowed on the lake. Always check the current ODFW regulations before fishing. Additionally, ice fishing may be a possibility when access is available.
North Twin offers quiet, primitive camping in the pines, a good swimming beach, a dirt boat ramp, and other excellent fishing opportunities nearby. North Twin C. G. has latrines, no drinking water, and charges a fee. The closest resort is at South Twin.