2027 Denver Colfax Marathon - May 16 Countdown

Q: When is the 2027 Denver Colfax Marathon and what time does it start?

The 2027 Colfax Marathon is on Sunday, May 16, 2027, the centerpiece of the May 14-16 race weekend in Denver. The full marathon starts early at 6:00 a.m. Mountain Time in City Park, beside Ferril Lake. The early gun is deliberate: it gets runners moving before the mile-high sun and midday heat build, so plan to be at the start line in the dark.

Q: How does the altitude affect the Colfax Marathon?

This is the race's defining factor: Colfax is run at 5,280 feet (1,609 m) — exactly one mile above sea level — making it one of the highest big-city marathons in the U.S. The thinner air holds roughly 17% less oxygen than sea level, so sea-level runners almost always feel it. The race's own medical advice is to arrive 2-3 days early if you can, drink noticeably more water, go easy on alcohol, and start conservatively rather than chasing a sea-level pace.

Q: Is the Colfax Marathon a Boston qualifier?

Yes. The Colfax Marathon course is USATF-certified and a Boston Marathon qualifier, so a qualifying time run here counts toward Boston entry. That said, the altitude makes it a tough place to chase a fast time — only about 2.5% of finishers qualified for Boston in 2026 (3.6% in 2025), well below flat sea-level qualifier races. Use our Boston qualifying calculator to check your standard.

Q: What is the Colfax Marathon course like?

It is billed as the ultimate urban tour of Denver. Starting and finishing in City Park, the route runs west down Colfax Avenue past the State Capitol, threads through Denver Fire Station No. 1, passes through Empower Field at Mile High twice, and loops around Sloan's Lake with combined downtown-and-mountain views. There's a fast 'Screaming Downhill' descent through Lakewood late in the race before a riverside return. Total climb is modest at about 690 ft (211 m).

Q: What is the time limit for the Colfax Marathon?

The full marathon has a 6-hour course time limit, an average of about 13:44 per mile (8:32 per km). Runners who fall behind that pace at checkpoints may be asked to stop or moved to the sidewalk for safety as roads reopen. If you're cutting it close, our pace calculator can help you plan a finishing pace with margin — and remember to add buffer for the altitude.

Q: How do I register for the 2027 Colfax Marathon and what does it cost?

Registration is handled through the official site at runcolfax.org (powered by Race Roster) and typically opens in August the year before, with the lowest prices in the earliest pricing tier and the fee rising as the race fills. Exact 2027 prices had not been published as of mid-2026, so check the official registration page once it goes live and sign up early for the best rate.

Q: What should I wear for the Colfax Marathon weather?

Mid-May mornings in Denver are cool and dry — expect a start around 46°F (8°C) that warms quickly. Dress for the chilly 6 a.m. gun with throwaway gloves and a long-sleeve you can ditch by Sloan's Lake. Because the air is dry and the high-altitude sun is strong once it's up, pack sunscreen, a visor or hat, and plan to take in more fluids and electrolytes than you would at a sea-level race.

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Race Information

Race	2027 Denver Colfax Marathon - May 16
City	Denver
Date	2027-05-16 at 06:00
Time Limit	6 hours
Cutoff pace	8:32/km
Timezone	America/Denver
Official Site	Colfax Marathon
Registration	Register

Race Day Weather

Average Temperature	12.2°C / 54°F
Humidity	50%
Wind	20.3 km/h
Rain Chance	41%
Typical Conditions	Cool, dry mid-May Denver morning — a crisp 6 a.m. start near 46°F / 8°C under thin, high-altitude blue sky, warming fast and with strong UV once the sun is up

What to Prepare: The 6 a.m. start is chilly at altitude, so wear throwaway gloves and a long-sleeve you can shed by mile 6. The mile-high air is dry and the sun is intense once it clears the skyline — carry electrolytes, drink more than you would at sea level, and pack sunscreen and a visor.

Based on historical averages for race week. Use our Weather Score Calculator and What to Wear Guide for personalized advice.

Wind Impact on Race Day

Wind at 20.3 km/h can affect your marathon pace by 5-15 seconds per kilometer. Headwinds slow you down exponentially — a 20 km/h wind costs more than twice a 10 km/h wind.

Calculate your wind-adjusted pace →

Race-Week Climate

Based on 20 years of race-week weather (2005-2024), MERRA-2 reanalysis

	Cooler	Typical	Warmer
Temperature	5.5°C	12.9°C	18.2°C
Dew point	-4.2°C	0.4°C	4°C

Wet-day chance: 41% Runnability: 83/100

Data: NASA POWER (MERRA-2 reanalysis), NASA Langley Research Center

Course Profile

Course Type	City point-to-loop
Elevation Gain	211m
Terrain	Road and paved river trail (city avenues, lakeside paths, one fast downhill section)
Profile	An urban tour of Denver run at 5,280 ft (1,609 m) — one of the highest big-city marathons in the U.S., where the thin mile-high air is the real difficulty even though the road profile is moderate. The course starts and finishes in City Park beside Ferril Lake, heads west down Colfax Avenue (billed as one of America's longest commercial streets) past the State Capitol and Civic Center, ducks through Denver Fire Station No. 1, and follows the Cherry Creek and Platte River trails through Empower Field at Mile High — which runners pass twice. The middle miles loop around Sloan's Lake with downtown-and-mountain views, push west through Lakewood neighborhoods, then drop on a 'Screaming Downhill' stretch with panoramic Rocky Mountain skyline views before a riverside trek back to a City Park finish. Total elevation gain is modest at roughly 690 ft (211 m), but the altitude itself thins oxygen by around 17% versus sea level, so sea-level runners should arrive 2-3 days early, hydrate aggressively and pace conservatively. USATF-certified and a Boston qualifier, though the altitude keeps the BQ rate low (about 2.5% of finishers qualified in 2026).
Boston Qualifier	Yes — Check your BQ time

Prepare for 2027 Denver Colfax Marathon - May 16

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Featured In

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Frequently Asked Questions

When is the 2027 Denver Colfax Marathon and what time does it start?

The 2027 Colfax Marathon is on Sunday, May 16, 2027, the centerpiece of the May 14-16 race weekend in Denver. The full marathon starts early at 6:00 a.m. Mountain Time in City Park, beside Ferril Lake. The early gun is deliberate: it gets runners moving before the mile-high sun and midday heat build, so plan to be at the start line in the dark.

How does the altitude affect the Colfax Marathon?

This is the race's defining factor: Colfax is run at 5,280 feet (1,609 m) — exactly one mile above sea level — making it one of the highest big-city marathons in the U.S. The thinner air holds roughly 17% less oxygen than sea level, so sea-level runners almost always feel it. The race's own medical advice is to arrive 2-3 days early if you can, drink noticeably more water, go easy on alcohol, and start conservatively rather than chasing a sea-level pace.

Is the Colfax Marathon a Boston qualifier?

Yes. The Colfax Marathon course is USATF-certified and a Boston Marathon qualifier, so a qualifying time run here counts toward Boston entry. That said, the altitude makes it a tough place to chase a fast time — only about 2.5% of finishers qualified for Boston in 2026 (3.6% in 2025), well below flat sea-level qualifier races. Use our Boston qualifying calculator to check your standard.

What is the Colfax Marathon course like?

It is billed as the ultimate urban tour of Denver. Starting and finishing in City Park, the route runs west down Colfax Avenue past the State Capitol, threads through Denver Fire Station No. 1, passes through Empower Field at Mile High twice, and loops around Sloan's Lake with combined downtown-and-mountain views. There's a fast 'Screaming Downhill' descent through Lakewood late in the race before a riverside return. Total climb is modest at about 690 ft (211 m).

What is the time limit for the Colfax Marathon?

The full marathon has a 6-hour course time limit, an average of about 13:44 per mile (8:32 per km). Runners who fall behind that pace at checkpoints may be asked to stop or moved to the sidewalk for safety as roads reopen. If you're cutting it close, our pace calculator can help you plan a finishing pace with margin — and remember to add buffer for the altitude.

How do I register for the 2027 Colfax Marathon and what does it cost?

Registration is handled through the official site at runcolfax.org (powered by Race Roster) and typically opens in August the year before, with the lowest prices in the earliest pricing tier and the fee rising as the race fills. Exact 2027 prices had not been published as of mid-2026, so check the official registration page once it goes live and sign up early for the best rate.

What should I wear for the Colfax Marathon weather?

Mid-May mornings in Denver are cool and dry — expect a start around 46°F (8°C) that warms quickly. Dress for the chilly 6 a.m. gun with throwaway gloves and a long-sleeve you can ditch by Sloan's Lake. Because the air is dry and the high-altitude sun is strong once it's up, pack sunscreen, a visor or hat, and plan to take in more fluids and electrolytes than you would at a sea-level race.