Always good to hear when people go to Yellowstone. Awesome place. A few suggestions/tips:
- Lodging: You're only a month away. Lots of places in/near the park are booked solid by now. Go online and/or call very soon to get lodging.
- Whether there will be wall-to-wall people in mid-June: Ummm, kinda yes. We went in mid-June and it was crowded, but better than July/August. Visit the famous places (Old Faithful, Grand Canyon of the Yellowstone, Mammoth, the Geyser Basins) early morning and/or early evening. Not only much less crowded, but also prettier with the softer emerging/fading sunlight. These tourist spots are famous for a reason...because they're amazing...so avoid the crowds but don't avoid the sites. Then hike during the middle of the day. Not a good idea to hike in the dark out there; the big dudes use the trails at night. Once you're a mile or so down almost any trail (with a few exceptions such as Mt Washburn) you'll see how uncrowded Yellowstone can be.
- In June there's still lots of snow up high. Some of the high passes might be "closed". Check with the backcountry rangers if you plan on doing a high elevation hike. Probably a good idea to check with the rangers before doing any hike this time of year just to avoid any unpleasant surprises (excessive flooding, trail closed due to bears, etc)
- If you want to see lots of wildlife, follow this secret: open your eyes. They're everywhere. Yellowstone is a zoo without cages. The best spots are Lamar Valley and Hayden Valley dusk and dawn. Bring binoculars.
- Watch out for the "Yellowstone Rollers", which are what they call the daily afternoon thunderstorms. It's a good show. Just be in a safe spot to enjoy them.
- Resign yourself to the fact that you will get caught in a bison-jam or a bear-jam. Peple's driving habits may not be to your liking at those times. Just accept it. There are worse places to be stuck in traffic. Just pull over, look at your pictures on your camera, enjoy the scenery, have a snack, whatever. Turn it into something good.
This website is a great resource. Lots of info on all things Yellowstone.
Have fun. Please post your photos.