Boulder Sunset Triathlon

Boulder, United States · August · Independent (BBSC Endurance Sports)

Same event, sprint distance: see its rating

Course: 1.5 km (0.9 mi) swim, 42.5 km (26.4 mi) bike, 10 km (6.2 mi) run. 1,500 m (0.93 mi) / 26.4 mi (42.5 km) / 10 km (6.2 mi)

Boulder Sunset Triathlon: boulder reservoir at dusk with the front range behind it (winter view, venue not race day)Photo is not from race dayYuya Sekiguchi, CC BY 2.0
Boulder Reservoir at dusk with the Front Range behind it (winter view, venue not race day). Photo via Wikimedia Commons.

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

3.0Good

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: Tough

  • 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 friendlyDoable3.2

    1,500 m (0.93 mi) swim at altitude, a 42.5 km (26.4 mi) open-road bike and one bike aid station. · Low confidence

Course traits, not part of the score

  • PR potentialAverage3.0

    Altitude, wind and a gravel run slow times. · Low confidence

Swim

4.0Very good

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 easeModerate3.2

    1,500 m (0.93 mi), with the first half into the sun. · 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

1.5Poor

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 speedFast3.5

    Smooth roads, but wind slowed 2019. · Low confidence

  • Bike flatnessMostly flat3.5

    Marketed as flat; a 2014 racer called it mildly hilly. Elevation is not published. · Low confidence

  • Bike simplicitySome technical parts3.4

    A 2014 racer reported several tight right-hand turns. · Low confidence

Run

2.9Good

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 conditionsModerate3.1

    Sandy gravel over 10 km (6.2 mi) at altitude on a late-August morning. · Low confidence

Course traits, not part of the score

  • Run flatnessMostly flat4.1

    Packed dirt loop of the reservoir; elevation is not published. · Low confidence

Conditions

3.7Very good

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

3.0Good

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 600 athletes
Entry fee
About $140
Distances (non-standard)
1.5 km (0.9 mi) swim, 42.5 km (26.4 mi) bike, 10 km (6.2 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.

Official race website (bbscendurance.com)

What racers and reviewers say

  • 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.

  • Cyclizing (Boulder Sunset race report, 2019)Raced 2019 · blog · Mixed

    Olympic-distance racer who wore a wetsuit. Reservoir construction changed the transition layout, volunteers did not direct him well to the run exit, a boat blocked the first buoy and warm-up was cut short. Wind made the bike a grind. Finished 7th overall.

  • 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

Pages we used for facts and ratings. See how we rate.

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