For blackflies, a headnet prevents most people who have the propensity to go insane when under attack, out of the tent. (Although eating can be a challenge.)

On the Deet - if you can find it in a pump spray, get it. BFs love ears and the hat line! One pump or less for each ear and the forehead (shielding eyes and mouth), then spread it to other exposed areas with the back of your hand. It keeps your hands/fingertips DEET free. DEET eats certain types of plastics like cameras and the like and tastes terrible.

BFs are snow-melt dependent. Skeets just need moisture.

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Look for lakes with few or well disbursed campsites, cross your fingers and have a fallback or two in mind.