There can be a big change from early May to late May.

In general, I’d say weather should be mild (but that’s not a guarantee) while a lot of trails will be pretty muddy. Some snow will be lingering around at higher elevations too. I’m very much a fair weather hiker and tend to save bigger hikes until after Memorial Day.

If you do hike in May, just make sure to stay on the trail even if it means walking through the mud. A lot of habitat damage happens when enough people step off trail to avoid mud. This is especially true in the alpine zone.