Midges are one of the most prolific food sources in all of the Lehigh Valley streams, and they are available all year long. Check out this really good video from RIO about fishing midges in winter. As a side note, the Al's Rat (fly), is probably the best midge pupa imitation locally. Al's Rat was designed by local fly fisherman Al Miller who fished the Little Lehigh 6 days a week for years.
Midge Fishing Winter: