At the moment, it looks like Gardiner (north gate of Yellowstone) will be getting some nice weather from mid May almost to the end of the month. However, the Beartooth Mountains have always gotten a significant amount of rain in May. So my advice is to bring along some warm clothing and some good rain gear for you and your camera gear, just to be safe. I live 60 miles NE of Slough Creek in MT and it's 40 degrees and raining right now. We also have quite of bit of rain and even some snow in the forecast for the next 10 days. So here's my best advice.... pack for ugly weather and if it turns out to be nice while you're in the Park, be happy and count yourself lucky. May and June are, historically, the two wettest months of the year in the GYE. So ya gotta expect some rain. The mountain snow pack is running off right now, so when you're driving in the Park or if you intend to go hiking, be sure to watch closely for any rising river, stream and/or for any falling rocks that have the potential for blocking/washing out roads, camp sites and hiking trails. As a general rule, the Park tries to post a notice at the trail head if the trail is impassible or closed. But you can't always count on that since mountain weather often changes fast and very unexpectedly.
The mountains snowpack was, reportedly, over 120% in March. So the ground is very saturated. In fact, I doubt if the runoff will be completely over until the end of June or early in July. Ditto for the rivers/streams that are in the northern end of the Park. On a cheerier note, the wildlife in the GYE is not only abundant right now, they're also friskier than ever. After such a brutal winter, they must be lovin' the warmer weather, rain and lush vegetation. As for me, I could do without some of that lush vegetation. We'll probably have to mow our 5 acres of meadow grass at least 4 times before we even go to the Park in mid June. Argh...
