COLORADO - Couloir season is a narrow window of time between April and June (sometimes July). A lot of snow melts off the high peaks as Springtime temperatures warm, but some remains tucked into mountainsides and it's climbable with the right equipment.
Weather is critical to couloir season. You want your crampons to bite and that requires firm snow. That requires daytime temperatures above freezing with subfreezing nighttime temperatures.
Couloir season is rarely about the summit. It's about the route, the climb, the process, and friends.
If it's your first couloir climb go with experienced friends, choose a lower angle route, and get the right gear. I recommend wearing a helmet on the busier routes.