This chart gives a basic overview of the most common major hatches in Montana rivers, as well as the general range of sizes for each insect. The hatching times are approximate, and will vary somewhat from river to river, and also due to local conditions; cool weather tends to delay and draw out hatches, while hot weather will have hatches occurring earlier in the season, and they will often be of shorter duration. As always, consult with a local fly shop or other sources for current conditions.
