Boulder Sunset Triathlon
Boulder, United States · August · Independent (BBSC Endurance Sports)
Course: 0.8 km (0.5 mi) swim, 27.8 km (17.3 mi) bike, 5 km (3.1 mi) run. 750 m (0.47 mi) / 17.3 mi (27.8 km) / 5 km (3.1 mi): the bike is longer than a standard 20 km (12.4 mi) sprint
Why people love it
- Rolling swim start in a reservoir, with kayaks to rest on and colour caps for nervous swimmers
- Sprint has a beginners wave at 07:52
- Swim, transition and finish share one reservoir lot
- Water ran 23 to 25 °C (73 to 77 °F) in reports, so wetsuits are usually legal
- Packed dirt run with water and Gatorade about every 1.6 km (1 mi)
Watch out for
- Bike roads are open to traffic; you ride on the shoulder
- Wind has slowed the bike, notably in 2019
- Altitude is about 1,600 m (5,250 ft), and the run is on sandy gravel
- Sprint bike is 27.8 km (17.3 mi), longer than a standard 20 km (12.4 mi) sprint
- Despite the name it is a morning race; no race-morning registration, and packet pickup is off-site
Race
How racers feel about it, how well it is run, and how it treats a first timer. Counts for 30% of the overall score.
Toughness: Moderate
- Racer satisfactionLoved3.7
Four athlete reports from 2014 to 2022 are mostly positive, though one 2019 Olympic racer hit course problems. · Low confidence
- OrganizationWell run3.5
Detailed 2026 athlete guide and rolling start, but 2019 brought a confusing transition, poor run-exit direction and a boat on the first buoy. · Medium confidence
- First timer friendlyFriendly4.2
750 m (0.47 mi) swim with a beginners wave, colour caps and kayak rests; open roads and altitude are the cautions. · Low confidence
Course traits, not part of the score
- PR potentialAverage3.2
A 2014 racer averaged 35.6 km (22.1 mi)/h (22.1 mph); altitude, wind and a sandy run limit times. · Low confidence
Swim
Wetsuit odds, water temperature, calm, and the experience of the start. Counts for 16% of the overall score.
- Wetsuit legalUsually3.6
USA Triathlon limit is 25.6 °C (78 °F). Late August water ran 23 to 25 °C (73 to 77 °F), usually legal but close. · Medium confidence
- Water temperatureComfortable4.3
Reported 22.8 °C (73 °F) in 2022, 23.3 °C (74 °F) in 2014 and 25.1 °C (77.1 °F) a week before 2026. · Medium confidence
- Calm waterSome chop3.4
Open reservoir with no chop reported, but a 2017 racer found the swim very physical. · Low confidence
- Swim easeModerate3.4
750 m (0.47 mi); sun glare on the first half. · Low confidence
- Swim experienceGreat3.6
The first half faces the sun, which hurts sighting; the 2026 rolling start should ease crowding. · Medium confidence
- Swim supportAbundant4.5
Organiser lists boats, kayaks you may rest on, lifeguards, colour caps for nervous swimmers and a beginners wave. No athlete has confirmed it. · Medium confidence
Bike
Road surface, closures, scenery and wind. Counts for 18% of the overall score.
- Road surfaceGood3.8
Organiser lists concrete and asphalt only; no one has complained about the surface. · Low confidence
- Road closuresMostly open1.5
Roads stay open to traffic and riders use the shoulder, per the 2026 athlete guide. · High confidence
- Bike sceneryBeautiful3.6
Rural roads north of Boulder with Front Range views; few athletes describe them. · Low confidence
- WindSome wind2.6
Wind made the 2019 bike a grind, though a 2017 racer rode a strong tailwind east. · Medium confidence
Course traits, not part of the score
- Bike speedFast3.6
A 2014 racer averaged 35.6 km (22.1 mi)/h (22.1 mph); wind helps or hurts. · Low confidence
- Bike flatnessMostly flat3.6
Marketed as flat; a 2014 racer called it mildly hilly. The 27.8 km (17.3 mi) bike is longer than a standard sprint. · Low confidence
- Bike simplicitySome technical parts3.4
A 2014 racer reported several tight right-hand turns. · Low confidence
Run
Crowds, aid stations, conditions underfoot and scenery. Counts for 13% of the overall score.
- Crowd supportDecent2.8
Small crowd on a reservoir loop; athletes cheered each other in 2022. · Low confidence
- Aid stationsGood3.8
Water and Gatorade about every 1.6 km (1 mi) on the run; Olympic bike has one aid station. · Medium confidence
- Run sceneryBeautiful3.9
The run circles the reservoir with Flatirons views; little athlete detail. · Low confidence
- Run conditionsModerate3.4
Sandy gravel, but only 5 km (3.1 mi). · Low confidence
Course traits, not part of the score
- Run flatnessMostly flat4.1
Packed dirt, mostly flat 5 km (3.1 mi). · Low confidence
Conditions
Air temperature, how predictable the weather is, setting, and spectating. Counts for 13% of the overall score.
- Air temperaturePleasant3.9
Starts 07:15 to 07:35; forecast 27 °C (80 °F) by midday in 2026. · Medium confidence
- Weather reliabilityReliable3.6
Dry late-summer mornings, with the race done before typical afternoon storms. Wind is the usual issue. · Low confidence
- Venue beautyLovely4.1
Reservoir with a Front Range backdrop. · Medium confidence
- Spectator friendlyEasy3.5
Swim, transition and finish share one lot; the bike and run spread out. · Low confidence
Course traits, not part of the score
- Low altitudeHigh altitude1.2
About 1,600 m (5,250 ft) above sea level. · High confidence
Stay and travel
Hotels, walkability, getting there, and the town around the race. Counts for 10% of the overall score.
- Hotel availabilityBook early3.4
Boulder is busy in late August when the university term starts. · Low confidence
- Hotel valueNormal3.0
Boulder is pricey, but no rates were found. · Low confidence
- WalkabilitySome driving3.4
Park in the reservoir overflow lots and walk to transition; hotels are 5 to 8 km (3 to 5 mi) away. · Low confidence
- Travel easeEasy3.6
Denver International is about 55 km (34 mi) away, roughly an hour by car. · Medium confidence
- LogisticsSome complexity3.3
One venue and transition, but packet pickup is off-site Thursday or Friday, or race morning for $10. · Medium confidence
- Town and foodGreat4.6
Boulder has a strong food scene and outdoor shops. · Medium confidence
Key facts
- Location
- Boulder, Colorado, United States
- Typical month
- August
- Latest or next date
- 29 August 2026
- Organiser
- Independent (BBSC Endurance Sports)
- Field size
- About 319 athletes
- Entry fee
- About $140
- Distances (non-standard)
- 0.8 km (0.5 mi) swim, 27.8 km (17.3 mi) bike, 5 km (3.1 mi) run
- Cutoffs
- Swim 08:45, Bike 10:30
- Swim venue
- Boulder Reservoir (reservoir)
- Water temperature
- 22–25 °C (72–77 °F)
- Wetsuit
- Legal
- Swim start
- rolling (three swimmers every 5 seconds in 2026)
- Run shade
- Little
- Air temperature
- 13–28 °C (55–82 °F)
- Humidity
- Dry
- Altitude
- 1,600 m (5,250 ft)
- Nearest airport
- Denver International (DEN), 55 km (34 mi) away
- Where to stay
- Boulder, Longmont
- Booking
- Book Boulder hotels early in late August. Packet pickup at Arvada (Thu) and Westminster (Fri), or race morning with a $10 fee 05:30 to 07:20; no race-morning registration.
What racers and reviewers say
- Felix Wong (Boulder Sunset Triathlon, 2014)Raced 2014 · blog · Mixed
Sprint: 28:38 swim without a wetsuit in 74 °F (23.3 °C) water, a leaking goggle mishap, then a 17.3 mile (27.8 km) bike at 22.1 mph (35.6 km/h) on a mildly hilly course with tight right turns, and a 5K on sandy gravel in 23:30. 89th of 319. Mixed on the swim but called it not a bad day.
“Today was not a bad day”
- Cyclizing (Boulder Sunset race report, 2017)Raced 2017 · blog · Positive
Racer's third podium-chasing race in the BBSC series, finishing third. The swim was very physical with sun glare on the first half; a strong tailwind on Nelson gave him about 35 mph (56 km/h). Reversed wave order let family watch. Very positive.
- Colorado Triathlete (Boulder Sunset marks the end of summer racing, 2022)Raced 2022 · article · Positive
Collegiate sprint winner's report from 28 Aug 2022: water about 73 °F (22.8 °C), wetsuit legal and comfortable either way, bike toward Highway 36 and Neva Road with some early mechanicals, a sprint run of 3 miles (4.8 km) around the reservoir. Quiet focus before the start and cheering during the run.
- BBSC Endurance Sports (Boulder Sunset race page, 2026)Raced 2026 · article · Positive
Official page: Olympic 1,500 m (0.93 mi) / 26.4 mi (42.5 km) / 10 km (6.2 mi); sprint 750 m (0.47 mi) / 17.3 mi (27.8 km) / 5 km (3.1 mi). Starts 07:15 Olympic and 07:35 sprint; cutoffs swim 08:45, bike 10:30, run 12:00. Calls it a beginner favourite for its flat bike and packed dirt run. Organiser source.
- BBSC Boulder Sunset 2026 athlete guideRaced 2026 · article · Positive
Official guide: rolling swim start with three swimmers every five seconds, safety boats, kayaks you may rest on, colour caps for anxious swimmers, all bike roads open to traffic, 1 bike aid station on the Olympic, run aid about every mile (1.6 km), packet pickup Thu and Fri off-site or race morning for $10, water 77.1 °F (25.1 °C) a week out.
Show 1 more
- running.life (Boulder Sunset listing)Raced 2026 · aggregator · Mixed
Listing for 29 Aug 2026 at Boulder Reservoir with sprint, Olympic, duathlon, aquabike and relay options, organised by BBSC. Gives no course data and mislabels a sunrise swim, so used only for date and venue.
Raced Boulder Sunset Triathlon? Your notes on the course, conditions and logistics help the next athlete decide.
Sources
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