Thunder Mountain Road Climb
- long (3.3 km)
- 2.0 mi
- long (3.3 km)
- of climbing (236 m)
- 774 ft
- of climbing (236 m)
- average grade
- 7.2%
- average grade
- steepest 500 m
- 13.2%
- steepest 500 m
Elevation profile
From 4,081 ft at the bottom to 4,856 ft at the top. Grades are averaged over each half kilometre, from USGS elevation data, so short ramps can be steeper than they show.
Weather at the top of Thunder Mountain Road this week
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Is it safe to bike up Thunder Mountain Road?
We don't rate roads as safe or unsafe: crash counts can't say how risky a ride is, and roads people like to ride draw more riders, so they see more crashes. What the records show: no bike crashes were reported along the climb from 2021–2025.
Common questions about Thunder Mountain Road
- How long and steep is the Thunder Mountain Road climb?
- 2.0 miles (3.3 km) at 7.2% on average, climbing 774 ft (236 m) from 4,081 ft to 4,856 ft. The steepest half kilometre averages 13.2%. That makes it a Category 3 climb.
- Where does the climb start and finish?
- It starts at 40.22979, -120.44162, where Thunder Mountain Road leaves Route 395, and ends where the road ends at 40.21433, -120.46475.
- Is Thunder Mountain Road paved?
- Yes, by its OpenStreetMap tags.
- How is the category worked out?
- From the climb's shape only: length in metres × average grade (%) of 16,000 or more for Cat 3, 32,000 for Cat 2, 64,000 for Cat 1 and 80,000 for HC. It describes how hard the climb is, not traffic or crashes.
- Where does this data come from?
- The climb is found from OpenStreetMap roads and USGS 3DEP elevation (every climb, not a list of famous ones). Access is from OpenStreetMap tags; gates and closures change, so obey posted signs. Crash counts are police reports in the California Crash Reporting System (CCRS) on data.ca.gov, counted where their map location is within 100 ft of the climb. The forecast is from the National Weather Service.
Other climbs nearby
- Shane LaneCat 3 · 0.7 mi at 16.1% · 581 ft · starts 2.6 mi away
- Wray RoadCat 3 · 1.1 mi at 9.4% · 531 ft · starts 4.3 mi away
- Janesville-GradeCat 2 · 5.0 mi at 7.1% · 1,893 ft · starts 5.2 mi away
- Milford GradeCat 2 · 5.6 mi at 6.1% · 1,831 ft · starts 5.7 mi away
- Lloyd's View DriveCat 3 · 1.6 mi at 8.2% · 692 ft · starts 6.2 mi away
- Diamond Mountain Motorway near SusanvilleCat 3 · 1.8 mi at 7.1% · 689 ft · starts 8.7 mi away
- Indians Road from Elysian Valley RoadCat 3 · 2.7 mi at 5.4% · 784 ft · starts 9.0 mi away
- Pierce Creek Motorway near SusanvilleCat 2 · 4.3 mi at 5.8% · 1,325 ft · starts 11 mi away
Found from OpenStreetMap roads and USGS 3DEP elevation; ranked on shape only. Category 3: length in metres × average grade (%) of 16,000 or more for Cat 3, 32,000 for Cat 2, 64,000 for Cat 1 and 80,000 for HC. It describes how hard the climb is, not traffic or crashes. Crashes: bike crashes reported within 100 ft of the climb, 2021–2025, from the California Crash Reporting System (CCRS), counted only where the report has map coordinates. Weather: National Weather Service. Access from OpenStreetMap tags; obey posted signs. How the data works.