Look into a section of the gutter from a safe vantage point — a stepstool or a quick look from the edge of the roofline on a single-story. If debris looks light and loose, you're good to proceed. If it looks wet, dark, and compacted, schedule for a dry day. Blowing wet debris creates a mess on your siding and doesn't clear the gutter — it just redistributes the problem.
Ideally, wait 48 hours after rain before cleaning. If you've had a dry week of sun, debris dries out significantly even if it was wet recently.