Here in the Pacific NW, it's hard to say if we get enough hot weather to make Habanero peppers as intensely hot as they could be, but there are ways to help. Heat up the soil by covering the ground with black plastic about a week before planting. Find the sunniest spot in your garden, and if you can place your peppers where they'll get reflected heat (off walls or fences), all the better. When the nights are still cool (60 or below), consider placing plastic-wrapped cages around the pepper plants or walls-of-water. Finally, keep water to a minimum, i.e. water deeply then let the soil dry completely before watering again.