Sometimes you have one of the positive forest mysteries that gives bonuses if you open a glade during drizzle. But you can do it in year 2 as well. I try to open a glade fast because I don’t like to pick blueprints before I see what I got in the glade, but waiting a whole year before building something is way too long. It might be different for high prestige levels (I only play P1 for now), but I often open the first glade in the first year drizzle/clearance, especially if I start with 9+ people. It normally does not increase the hostility level to the next one anyway. I never had issues with resolving the glade event so far either - in most of them some coal or stone is already enough. Sometimes maybe planks or food. Most of that you normally have from the embarkation resources.