Colorado's monsoon season turns Boulder afternoons into a predictable lightning and hail window each July through September — the mechanism and safety basics.

Boulder's summer thunderstorm cycle fires reliably between 1 and 7 p.m. — the meteorology behind the pattern and how to plan any outdoor ride around it.

When is it safe to hike the Flatirons above Chautauqua? A weather guide to afternoon lightning, sun and heat at elevation, seasonal trail conditions, and reading Boulder's foothills before you go.