Some helpful information about YSNP (some general items apply to GTNP also)
YNP is BIG!, about 45 miles E/W and about 65 miles N/S (2.2 mil. Acres total). The “figure 8 grand loop” road inside the park is about 140 miles around. The lower loop is 96 miles and the upper loop is 70 miles around and yes, it is bigger than the states of Rhode Island and Delaware combined.
Whatever time that you think you will need to see YNP you better double it, or to say it another way is that you will see one half as much as you planned on in the allotted time. The Bison think that they own the road (they do!) and will slow down the traffic to walking speed or stop all traffic for 1/4 mile or more blocking both directions of travel, the thermal attractions also tie up traffic and with a 5 month long summer tourist season that coincides with a 5 month long road construction season and a 45 MPH radar controlled speed limit it will take about a full day to see each loop and then you will only see the main attractions. In addition to the occasional construction delays they will also sometimes close whole sections of road (for uninterrupted night construction) between 10 PM and 8 AM in the morning, if you are running late and get caught at night in the wrong area it CAN be a LONG way around to your CG! (The entrance stations will have current construction information or go on line to check it out)
Then there is the elevation- YNP ranges from a low at Mammoth- 6239 ft to 7784 ft at Fishing Bridge or higher if you go hiking and there are passes on the grand loop road that are close to 8000 ft or so! Drink plenty of liquids and pace yourself when walking.
I recommend that you get up EARLY, leave the CG and be back by 4 or 6 PM have dinner and be sitting in your recliner drinking a cool one when your neighbor drags himself back to the CG at 8-10 PM. Remember that from mid May to mid July in YNP the sun doesn't set until about 9:00- 9:15 PM then there is a long and bright twilight.
Cell Phone Service- Only at the major visitor centers, otherwise non-existent!
Clothing- Especially in the early or late season it is not unusual to have a 30 or even the occasional 40 degree temperature change throughout the day. Dress with easily shed layers of clothing. Also dress in bright easily seen clothing. I am sure that we all have been to a sporting event, parade or Disney World etc. and we blink our eyes and our partner/child has disappeared. My DIL was born and raised in HI, you guessed it, every Xmas, b-day or Father's Day I receive a Hawaiian shirt. One of them is shiny black with 4-5 inch dia. bright flowers. Not many of them in Wyoming and in YSNP, that is what I wear. If your partner has on a Violet blouse and a Orange scarf with a Pink hat I guarantee that she will be the only one within the boundaries of either NP. It can save you a few anxious moments.
Water- Now I will have to contradict myself, at the altitude of YNP yes, drink lots of water! HOWEVER, be aware that the flush toilet restrooms are in the major tourist areas- Mammoth, Canyon, Fishing Bridge, Lake Hotel, Bridge Bay, Grant Village, Old Faithful, Madison Junction etc. The geyser basins and other thermal attractions areas only have pit toilets. I have seen the pit toilet line at the lower Geyser Basin (2 R/Rs) 25 or more feet long (bless the tour buses) So be smart about drinking your water and use the major tourist area R/Rs before leaving the area! I.e. “Never pass up a flush toilet!”
Sun- At YSNP altitude the Sun is intense (uv) have and apply sunscreen, wear that old floppy wide brim sun hat, wear Sunglasses!
If your luck is like mine Old Faithful will have just erupted when you get there and you will have up to a hour and 10 to 15 minutes wait for the next one. Tour the O/F Geyser basin while waiting. O/F INN is a must see, reportedly the largest LOG building in the U.S. (Meals in the O/F Inn dinning room are “A OK” also.
We have lived about 110 miles from West Yellowstone, MT since 1964, go to YSNP 3-4 times a summer (normally before Memorial Day and after Labor Day) and haven't seen it all yet! So don’t be discouraged that you didn’t have the time to see all of it. Just plan on coming back another time!
I honestly don’t mean to scare or discourage you but to give you a heads up as to what to expect! After all there was 4.1 million visitors in 2015! As far as I know we didn’t lose one of them. Except those who by their own stupidity step off the board walks into BOILING HOT water and ignoring the warnings about the WILD ANIMALS! That is called purifying the gene pool!
Now, for the early spring/late fall visitors, YSNP is closed to ALL wheeled traffic from mid November to mid March (Snow Machines, Snow Coach’s, Snowshoes, X-country Skiing etc only as of mid Dec to mid March) the first road to be plowed open in mid April is from West Y’stone, MT to Old Faithful. The last roads to be plowed is Norris to Canyon to Fishing Bridge, West Thumb south to GTNP. Other tourist venues are open AS the shelves are stocked, beds are made, winter debris cleaned up etc. All tourist venues are open by Memorial Day weekend the official opening.
Note I have seen on this blog and others about folks “day tripping” from YSNP to GTNP, it is done all the time (myself included) however remember this is BIG country and with the speed limits, animals and thermal attractions you will be doing a LOT of slow driving. From Grant Village Visitor Center (extreme S/E corner of the lower loop road) to Jackson, WY is about 80 miles with Coulter Bay being about 1/2 way, then from Grant Village you have to add the distance to your CG it will be a Long days trip!
A point of Coulter Bay (GTNP) clarification- there are two (2) CG’s at Coulter Bay, One the “Coulter Bay RV Park” a full service “RV Park” with FHU’S that takes reservations. The other is the “Coulter Bay Campground “ (FS CG) has no hookups and doesn’t take reservations. Both have about 300 sites and are basically across the road from each other.
The Gros Ventre FS CG in GTNP (about 5 miles north of Jackson and about 4 miles n/e toward the town of Kelly, on the right side of the road) is about 300 sites (including about 30 sites that are electric only) has no hookups and doesn’t take reservations.
When in the Jackson area I highly recommend seeing the Bar J Chuckwagon dinner show! If you go, MAKE RESERVATIONS and BE THERE EARLY TO PICK UP YOUR MEAL TICKETS/ TABLE SEATING ASSIGNMENTS! They seat you by when you show up to get your tickets NOT by your reservation number. Tim, their fiddle player has won the "Idaho state old time fiddle contest 9 times and the US open fiddle championship twice". If you decide to go you will sit at picnic type of bench seats/table, they get pretty hard, I recommend that you take along a blanket/pads to sit on. We day trip it there 2-4 times every summer just to see them! Disclaimer- We have no financial or other interest in the Bar J only that it will be the best $$ value for your money on your trip! Check out their website.
Also in Jackson check out the “COWBOY” bar, the bar stools are saddles and the # of Silver Dollars imbedded in the bar. The Wort Hotel Bar (just around the corner from the Cowboy Bar) also has Silver Dollars imbedded in the Bar.