Like other reports have said, the final mile for the road to the trailhead is fairly rough, though there are a few places you could park if you aren't comfortable going over those sections. The rest of the road you'll need to just stay vigilant and dodge the potholes. Couple sections had some washboarding.

There is a pretty nasty bathroom at the trailhead but it'll do in an emergency. The whole hike had a lot more bugs than I expected, but they weren't too much of a nuisance for us.

The trail itself had tons of wildflowers to see the whole way and lots of butterflies flying around. There aren't any sections of the trail without something beautiful to look at. Nearer to the top, there is still a little snow, but it was no problem to pass. I expect it will be melted pretty soon. We saw a couple groups of Marmots. One of them had one that looked like a baby. We also saw some Pikas and a couple friendly chipmunks.

I stayed overnight at Sauk Mountain for some photography.  

Road: In decent shape overall.  Though I have a high clearance vehicle I chose to park at the final bend and walk the remaining 1/4 mile or so to the trailhead.  2 cars at the trailhead at 7.30am on a Friday.

Trail: Great shape overall.  Some snow after you cross over to the other side of the mountain but not too difficult though hiking poles may be helpful.  Unfortunately there are some spots where switchback-cutting and its impacts were quite clear.  If you start early then you will be in the shade for most of the hike at this time of year.  It looked like the trail up is in shade until 9am or so (for now).

Wildflowers: Blooming on the southwest side for several varieties; on the north side (where snowmelt is still underway) wildflowers just getting started.  Regardless, the next 2 weeks or so should still be a prime window for wildflowers here.

Bugs: Virtually none at the trailhead and on the way up, but at the top they were a nuisance.  I had to use my headnet during the afternoon and early mornings.

Backpacking notes: Obviously no water along the trail unless you want to melt snow (which might only last another week or two).  There is a nice shaded area before the summit that works well for camping.

Sunset and sunrise were both amazing.  This hike is a jewel considering you reach 5,000+ ft with just a couple miles and 1,200ft gain.  

This is hands down our favorite early season North Cascades hike. The flowers are incredible right now—make sure you have the Seek app on your phone! The last 1/2 mile of the road is pot holey but small cars made it, and some parked down the road 1/8 mile. Some snow at the top but easy to cross as is not on a slope. The switchbacks are suffering from a lot of erosion from switchback cutters, and the trail is getting narrower each year, so PLEASE stay on the trail. Bring TP for the outhouse, which is not maintained. Plenty of parking at 9 am on a Friday.

Started the trail with some fog so could not see any views! Beautiful wildflowers on the trail!
Once we finished all the switchbacks is when the clouds started to clear a bit and we got a great view of the lake!

Perfect time to go now, wildflowers are insane!

We hiked the Sauk Mountain trail on a sunny Tuesday.  The road in has potholes, but nothing that can’t be handled by a regular car with careful driving.   The final, steep climb up to the parking lot is by far the worst.  This short stretch, only a couple of hundred yards at most, is very rough, with rocks, troughs and loose dirt.  Several people had opted to park along the road below this stretch.  However, in addition to Subarus, other SUVs and trucks, there were a few regular sedans in the lot, including a Tesla, so apparently the last stretch can be done without 4WD or high clearance.

We arrived at the trailhead at around 11:30 and snagged the last spot in the lot.  Several people arrived after us and had to park lower down.  The lot cleared out during the day, and by 3:00, only 6 cars were left.  

Predictably, we met a lot of people hiking out as we climbed the switchbacks, but we had the trail mostly to ourselves by the time we topped the ridge.  Opting for an afternoon hike was a good plan for avoiding the crowds at the top. 

The climb up the avalanche chute is very exposed, with only a couple of places to stop in the shade, and there is no water on the trail for dogs.  Fortunately, a light breeze kept the temperature comfortable for us and our dog wore her sun shirt to keep her cooler.  The switchbacks (all 22 of them) are generally in good shape, although there are a few loose, slippery places.  We saw one woman coming down one of these on her bottom to avoid slipping.  Good hiking shoes and poles are definitely helpful, especially on the descent. 

The summer wildflower bloom is in full swing along this section of the trail and it was a joy to stroll through the diversity of greenery and blooms, including valerian, cow parsnip, phlox, lupines, penstemons, tiger lilies and columbines. 

Over the ridge, a few snow patches are still melting out and the trail crosses several of these (see photo).  The path over the snow is clear and the snow was solid enough to walk on.  The final climb to the top is clear of snow, as is the top.

We were lucky to have a clear, 360-degree view from the top.  This was our fourth climb up this trail, but the first in which the view has not been obscured by clouds.  

We found a somewhat secluded spot for our late lunch and lingered for over an hour enjoying the view and identifying all the familiar peaks to the north, east, south and west.  We could even see the top of Mount Rainier far to the south.  A curious chipmunk and a pika scurried around while we watched.  Only a few other groups joined us and by the time we left, only one other hiker was left.  Just down from the peak, a big marmot watched us and whistled.  We met only two groups hiking in as we hiked out.

All in all, I would rank Sauk Mountain as one of the top hikes in the Bellingham area.  It is relatively short, delivers outstanding views right from the trailhead and offers a gently graded path up to the alpine.  The views from the top can’t be beat.  The only downsides are the crowds (this is a very popular trail all summer and fall) and the hot, southern exposure up the avalanche chute.