Heavy weather means low light. Summertime hatches seem to get more intense during these low fronts. Insects, especially Mayflies, ride the surface longer, especially when it remains calm. Without the sun and wind, emerging wings take longer to dry and therefore “Lift-off” gets prolonged.
Trout, even cautious big ones, seem more willing to risk rising for tiny morsels in low light. Below, some nice low light rainbow trout caught sight-fishing with small Pale Morning Dun dry flies, hook size 16 and 18. Low fronts, low light…your signal to head to the river with your rain jacket and dry flies.