Check the Lassen Volcanic National Park website for seasonal closures.
While only 2.5 miles each way, this trail has a 2000 ft elevation gain. Starting at 8000 ft near the parking lot, you start off with a steep climb that continues relentlessly from there until you get near the top. Then the trail turns into a very steep climb to the summit at over 10,000 ft.
The trail is well marked so you won't have much chance of getting lost. It is a very popular trail with plenty of traffic. It's almost entirely exposed with only a handful of partially shaded areas. It would be in your best interest to come up to Lassen a day or two before to get acclimated before attempting this run.