Cannabis clones need high humidity and warm, stable temperatures to root. Get those two variables right and most other small mistakes won't matter. Get them wrong and nothing else will save the cut.
Aim for 70 to 80 percent relative humidity. New cuttings can't pull water through their stems until roots form, so they rely on their leaves absorbing moisture from the air. Below 65 percent and they wilt. Above 85 percent and you invite mold, botrytis, and stem rot. A basic humidity dome with two or three vent holes sits right in that zone without any extra gear.
Temperature should stay between 72 and 77 degrees Fahrenheit at the leaf surface. Root zone temperature matters even more. Keep the medium at 75 to 80 degrees using a seedling heat mat under the tray. Cold medium stalls rooting more than anything else — even a perfect dome can't save cuttings sitting on a 62-degree garage floor.
Avoid temperature swings. A clone that sits at 80 degrees during the day and drops to 60 at night will root slowly or not at all. Stability beats perfection. Pair good environmental control with correct light levels and you've covered the three things clones actually need.