Depending on where in the state you’re going, the season may or may not be at its peak, but you’re likely to encounter them in May regardless. They breed in running water, not stagnant or still water, so that’s where they’ll be the most. I wear a mosquito net over a hat when I’m working in my garden. Bug sprays help, but they seem to find ears irresistible. Covering up is the best bet, and May isn’t so warm in NH that you’ll be uncomfortable in long pants and shirt sleeves. Edit: also, welcome and have fun!