Re: Montana in July
People closer will chime in I'm sure.. but July is usually a little early for hoppers.
But it's usually PMD season in a big way.
All the mayfly patterns Linehans mentions look good.. but, like above, that's out of my range. One thing I'd add is your favorite PMD emerger.
ETA: Hoppers always seem to work, but that's just not the peak..