Gandy Warm Springs is located near the Utah/Nevada border, just north of Garrison, Utah. It's a small natural pool just below Spring Mountain, and the water temperatures are just that - lukewarm.
Saratoga Hot Springs is a local warm spring, located in Saratoga Springs, Utah right on the NW edge of Utah Lake. It's is about 20 x 30 ft in size, and very shallow around 1-2 feet deep, surrounding by tall lakeside grass.
Red Hill Hot Springs is a popular soaking destination in central Utah, in Monroe. It consists of four pools, all fed by one very hot water source on top of the mound above the pools. Because this hot springs is free (and also on private property), it gets very crowded especially on weekends. The owners allow people to visit as long as the place is cleaned up after and not destroyed. This is a great place for families looking for a really nice hot springs that you don't have to hike it.
Spencer Hot Springs is located almost directly in the center of Nevada, about an hour west of Eureka, NV. This is one of Nevada's more popular hot springs, and consists of three soaking areas - two tubs and one natural pond. This remote area is dog friendly, has plenty of free camping, clothing is optional (half the people we saw were skinny dipping), and it's free to soak.
12 Mile (Bishop Creek) Hot Springs is one of Nevada's hidden gems that is oh, so relaxing. Nevada has more hot springs than any other state in the U.S., with more than 300 occurring naturally; most are found in Northern Nevada.
Meadow Hot Springs in Central Utah is a great family-friendly spot to hang out and soak in warm water. It's conveniently located right of I-15 and there's no hiking involved, so it makes for a great, quick soak when you are on a road trip. Meadow Hot Springs is located on private property in the middle of a cow pasture, but they do allow public access. There are a total of three pools to soak in, all around 100F degrees. The most popular pool is one of the smallest and closest to the parking area, and it is also the warmest. Each of the pools have algae in them, so it is wise to wear water shoes to keep from slipping on the rocks under water.
Baker Hot Springs is a small, natural hot springs located in Central Utah, not too far from Delta, Utah. The source of the hot springs is around 180F, but a trench helps the water flow down to three large tubs and cools off the further you are away from the source. The tub closest to the source is the hottest, the middle tub is, well in the middle for temperatures, and the furtherest is the coolest. However, you can "regulate" the temperature by using one of the provided rags to block out the hot water and let cold water from a pipe in.
Crystal Hot Springs is a natural hot springs in Northern Utah that ranges from 120-134 degrees F. The swimming pools are regulated so that you can soak in a range of temperatures from 98-105F. Crystal Hot Springs also contains the highest mineral content found in the world! It has roughly 46,000 mg/L - the average hot spring has closer to 1,000 mg/L. You'll notice this mineral content, as you lick your lips or wipe your hands over your face - it's very salty tasting. Get ready to soak in a 22,000 year old hot spring!
Maple Grove Hot Springs is located at the Northern end of the Bear River, along the scenic Oneida Narrows Reservoir in South Eastern Idaho. There are three large soaking tubs, plus a larger therapy pool. The tubs are formed from rock and mortar, and every pool offers a great view of the reservoir. This hot springs is not as well known as some of it's neighboring hot springs, so you'll see few people and tourists soaking here. There's no nearby restaurants, so its best to bring your own snacks or picnic lunch and the closest gas station is in Preston, ID. The water at Maple Grove Hot Springs is free flowing, sulphur free, and odor free, so you won't come out smelling like rotten eggs.
Lava Hot Springs is located in Idaho, about a 2 hour drive north of Salt Lake City. The natural, geothermal hot springs range in temperatures from 102F-112F degrees. The hot water is full of minerals, but has no sulfur, and therefor no bad smells of rotten eggs lurking in the air. Lava Hot Springs is open year round, but the best time to go, of course, is the Winter months. With five outdoor hot pools, the steam from the hot springs wraps around people and creates a very relaxing atmosphere. The red tents above provide shade on sunny days. Be sure to bring plenty of water and a snack to the hot springs - sitting for too long in hot water will dehydrate you and will make some people feel faint.