TLDR: ice and snow for the final mile- traction devices like microspikes really helpful and possibly also poles.

I did a trail run up the main Mount Si trail starting around 7:30am. There was a light drizzle and only one other car in the parking lot. I saw one hiker on my way up who had turned around short of the top.

Luckily for me the drizzle soon stopped. I began to see traces of snow in the woods about 2.8 miles from the trailhead and then snow and icy patches began right around 2.9/3.1 miles. The snow became increasingly thick and soon the trail was pretty much covered. I found microspikes extremely necessary for continuing and was very happy that I had brought mine plus a good jacket and waterproof hat.

It looked like fresh snow had fallen the night of 3/11/25 - and there were no footprints yet. By the time I was nearly to the somewhat flat area at the foot of the Haystack the snow had deepened to several inches of mostly fluff, speckled with rain and tree snow bombs… and a few blurred and (to me anyway) unrecognizable animal tracks. Snow plus all those lumpy boulders was pretty but made for tricky footing.

The views from this spot were great but the wind picked up, it began to snow and I hurried down into the woods before I could get too cold. Easy jog back down - pausing to remove my microspikes after about a mile of descent.

On my way out I counted 14 intrepid hikers ascending even though the weather shifted and turned to a steady rain. So, a pretty quiet day for Mt. Si!

We got to the trailhead around 8:30 a.m. and had no trouble finding parking. After a quick gear-up, we hit the trail. The first couple of miles were snow-free, but as we trekked higher, a thin dusting of snow started showing up, building up to about 3-4 inches by the boulder field. From the get-go, we were getting hit with nonstop snow bombs! We were expecting clouds and maybe some rain, but the weather turned out way better than we thought. With fresh snow covering everything, it became a beautiful winter wonderland hike!

Hiked it Sun Mar 9, very nice.  Mostly dry and snow-free but there's still packed, slushy snow for the last few hundred yards near the summit.  Weather turned colder Sunday afternoon and snow is in the summit forecast for almost every day of the coming week.  Pleasantly cool at lower elevations but mosquitoes are already coming out.  Be prepared for cold wind near the summit too.  Parking lot was about half full on Sunday.

Beautiful way to ring in March. Trail was very busy, but parking spots could be found in the lot and on the road. Negligible amount of slush at the top, and a few mosquitoes at the bottom.

Hiked Sunday afternoon 2-23-2025 for some winter conditioning. I arrived around 1pm and the parking lot was mostly empty. The rain was relentless from the jump. I recommend leaving extra clothes in your car, even if you have really fancy gear for similar conditions. I packed microspikes, but did not need them. There was only snow and some slushy ice near the very top of the hike (unless you are going back to the haystack). There were a lot muddy puddles, but I didn't experience any issues with traction or slips in any sections. Very easy to navigate the slushy ice near the top. I had the trail to myself most of the time due to the horrendous weather. It was really quaint. The summit had a pleasant breeze and the trees were blowing in the wind through the valley under sheets of PNW rain. A mellow Sunday afternoon.