Similar to Mailbox Peak Old Trail, Mount Si is famous in the I-90 corridor trail guides for being one of the more challenging options for a beautiful day hike. Make sure you bring your Discover Pass if you want to park at the Mount Si trailhead. We did Si on the first weekend over 90° and boy, did we feel it! The journey to the top consists of seemingly endless switchbacks and a 3100+ foot elevation gain, and although it is not nearly as steep as Mailbox, the trail felt much harder in the hot weather. This trail has heavy foot traffic throughout the year, so it was no surprise that we saw hundreds of hikers along the way, many of them training for Rainier by wearing heavy packs (I was so impressed–I’m definitely not quite there yet!). One of the perks of it being such a popular trail is that the path is well-maintained and is easy to follow.
We started off at a steady pace, but by the time we reached the halfway point about 2 miles in, we were sweating and taking lots of breaks. We had only brought about a liter of water each, and about a half mile from the top considered turning back because we were completely out. Luckily for us, we ran into a friend on her way down from the top, and she saved the hike by giving us another half liter! [Sidenote: The day after I hiked Mount Si, I went out to REI and bought a 2.5 liter water bladder, and have been using it for the majority of my hikes since. If you decide to tackle this trail, I highly recommend you bring more fluids than you think you’ll need, especially if it’s a hot day.]Once we got to the end of the trail, we sat down, had lunch, and watched the birds flit around asking for handouts from tired hikers. The views were top notch, and would have been even more spectacular had we braved the rock-climb up to the top of the infamous Haystack.
I would highly recommend Mount Si for anyone looking for a moderately challenging day hike, but I would definitely check weather conditions before you set out to do this trail–I enjoyed it, but it would have been better for us had the temperature been at least 15 degrees cooler. I hope to go back to Mount Si when it gets a little chillier in the fall, and definitely want to climb Haystack next time around!