Colfax Marathon training plan: course, start dates, and plan options
Denver, COMay 16, 2027
Every mile of the Colfax Marathon is run above 5,000 feet. The course sits between 5,172 and 5,533 feet as it works through Denver's City Park, Sloan's Lake and downtown, starting at 6:00 a.m. on the east side of Ferril Lake. The terrain is gentle. The air is the difficulty.
Answer a few questions, choose your plan, then create your account and subscribe to start training in Stride.
That distinction changes what training can and cannot fix. You can prepare your legs for 693 feet of climbing in a couple of long runs. You cannot prepare your lungs for 5,300 feet while living at 200. So the work here is split between the plan and the goal you set before you start it.
234 days to race day
Colfax Marathon · May 16, 2027 · about 33 weeks out
Your plan starts with your race and works backward. Every week lands on a real calendar, with race day at the end.
When to start training for the Colfax Marathon 2027
Race day is May 16, 2027, which is 234 days from today. Counting back from that date, here is when each length of build starts.
- 30-week buildStart October 18, 2026
- 24-week buildStart November 29, 2026
- 18-week buildStart January 10, 2027
- 16-week buildStart January 24, 2027
- 12-week buildshortest Stride acceptsStart February 21, 2027
You have about 33 weeks until race day, so there is still room for a full build. Stride reads the runway you actually have and maps every week from today to May 16, 2027.
Answer a few questions, choose your plan, then create your account and subscribe to start training in Stride.
Colfax Marathon course facts
- Course
- Mostly Loop · Rolling Hills · Road/Pavement
- Elevation gain / loss
- 693 ft gain, 694 ft loss
- Highest / lowest point
- 5,533 ft / 5,172 ft
- Marathon finishers
- 2,917 in 2026 (mid-size field)
- Boston qualifier
- Certified Boston qualifying course
- Finishers running a qualifying time
- 2.5% in 2026
- Typical race morning
- 46°F at the start, 73% humidity, partly cloudy
- Race day high / low
- 68°F / 40°F on average
Let’s find the plan for you.
Your race, current mileage, longest run, marathon experience, and available days decide the best fit. Stride maps the plan you choose to race day at the Colfax Marathon.
- Stride Run-Walk FinisherThree sessions a week with planned walk breaks, cover the full distance before race day.
- Stride First MarathonThe classic four-day first-marathon build: easy running and one weekly long run, no speedwork.
- Stride First Marathon PlusA first-marathon build with a little more volume and weekly race-pace miles.
- Stride 6-Day FinisherFinish your first marathon on frequency: six easy-leaning runs a week, no monster long runs.
- Stride 5-Day Pace BuilderFive days a week with race-pace runs before your long runs, built for a mid-pack time goal.
- Stride 6-Day RhythmSix days a week with three quality sessions, steady fatigue that teaches you to finish strong.
- Stride Time-Based FoundationFive time-based runs a week, mostly easy, the injury-averse way to a strong finish.
- Stride Time-Based BuilderSix time-based runs a week at a strict 80% easy / 20% hard split, chase a time goal without breaking.
- Stride 3-Day Cross-TrainThree runs plus two cross-training days over 24 weeks, marathon fitness on a busy schedule.
- Stride 3-Day QualityExactly three hard runs plus two mandatory cross-training sessions, every workout counts.
- Stride 6-Day CumulativeThe six-day cumulative-fatigue build with quality from week two, for PR chasers with a base.
- Stride Threshold 55The serious BQ/PR build to 55 miles a week: threshold work, medium-long runs, and 20-milers.
- Stride Threshold 70The high-mileage BQ/PR build to 70 miles a week for veterans with a deep base.
- Stride 2-Quality FlexTwo fixed quality sessions a week, everything else flexible easy running, fits any schedule.
Answer a few questions, choose your plan, then create your account and subscribe to start training in Stride.
Choose your Colfax Marathon training window.
Compare 12, 16, 18, and 20 weeks counted back from race day. The 18-week option includes the complete four-day schedule.
The course: a mile-high loop through City Park, Sloan's Lake and Empower Field
The Colfax Marathon starts and finishes in Denver's City Park and runs a mostly-loop route through Sloan's Lake, historic Lakewood, downtown and the length of Colfax Avenue. It passes through Empower Field at Mile High twice and goes inside Denver Fire Station #1, with what the race counts as roughly seven miles of rivers, lakes and bridges.
The elevation numbers are mild by Colorado standards: 693 feet of gain against 694 of loss over 26.2 miles, inside a band 361 feet tall. At sea level this would be a fast course. The 2.5% Boston qualifying rate in 2026 tells you what the altitude charges for it.
The 6:00 a.m. gun is not cosmetic. Denver in mid-May averages a high of 68F, the sun at that altitude is stronger than the number suggests, and starting in the dark buys you most of the race before the day heats up.
How to train for the Colfax Marathon
Train for the Colfax Marathon by building aerobic ceiling and by setting an honest altitude-adjusted goal. If you live near sea level, the 693 feet of climbing is not your problem; running 26.2 miles in air a mile up is. Plan for a slower goal pace than your flat-course fitness says you have earned.
In practice that means more volume at easy effort and fewer sessions chasing exact paces. Threshold work run by feel travels to altitude much better than threshold work run by watch. If you can get to elevation at all in the final block, even for a weekend, take it.
Two logistics that are really training. A 6:00 a.m. start means eating at around 3:30 a.m., so rehearse that breakfast on long runs rather than improvising it. And dry Colorado air pulls fluid out of you without the soaked shirt that normally warns you, so drink on a schedule instead of by thirst.
Getting in
Colfax has grown quickly. 2,917 people finished the marathon in 2026, up from 2,276 in 2025 and 1,095 in 2022, and it has not needed a lottery to manage that. Register through the race's own site. The expo is at Empower Field at Mile High, which is also the building you run through twice on race day.
Where does the Colfax Marathon get hard?
From about mile 20 along Colfax Avenue, when the altitude has taken more out of you than your splits show and the sun is finally up.
What is the weather like at the Colfax Marathon?
Mid-May race mornings in Denver run near 46F with humidity around 73% and partly cloudy skies, warming to an average high near 68F. The 6:00 a.m. start means a cold twenty minutes in the corral and a warm final hour. Train some long runs starting in the dark so the early alarm is routine by race week.
Is the Colfax Marathon a good Boston qualifier?
Colfax is a Boston qualifying course on paper and a poor one in practice. 2.5% of finishers ran qualifying times in 2026 and 3.6% did in 2025, and the rate has not reached 6% in any year since 2021. Altitude costs you minutes that a course with only 693 feet of climbing has no way to give back.
Is the Colfax Marathon a good first marathon?
It is a good first marathon if you live in Denver and a risky one if you do not. The profile is gentle, the field runs to a few thousand, and the 6:00 a.m. start keeps you ahead of the heat. The six hour limit is real, though, and altitude makes a first-timer's pace much harder to judge.
Colfax Marathon questions, answered.
How does altitude affect the Colfax Marathon?
It is the defining factor. The Colfax Marathon runs entirely between 5,172 and 5,533 feet, and runners arriving from sea level should expect to run slower than their flat-course fitness suggests, especially after mile 18. There is no way to fix that inside a training block, so adjust the goal instead.
Is the Colfax Marathon a good Boston qualifier?
No. Only 2.5% of Colfax finishers ran Boston qualifying times in 2026, and 3.6% did in 2025. The course itself is gentle, with 693 feet of climbing across 26.2 miles, but the altitude takes back more than the profile gives. Choose a low-elevation race if a qualifier is the goal.
What is the Colfax Marathon course like?
Gently rolling and thoroughly urban. It starts and finishes in Denver's City Park and runs Sloan's Lake, historic Lakewood, downtown and Colfax Avenue, passing through Empower Field at Mile High twice. Total climbing is 693 feet against 694 of descent, so no single hill decides your race.
What time does the Colfax Marathon start and how long do you have?
The marathon starts at 6:00 a.m. on the east side of Ferril Lake in City Park, and the course limit is six hours. That works out to about 13:44 per mile, tighter than many big-city races allow. Plan breakfast for roughly 3:30 a.m. and practice that timing during training.
Where does the Colfax Marathon get hard?
From about mile 20 along Colfax Avenue, when the altitude has taken more out of you than your splits show and the sun is finally up.
What is the weather like at the Colfax Marathon?
Mid-May race mornings in Denver run near 46F with humidity around 73% and partly cloudy skies, warming to an average high near 68F. The 6:00 a.m. start means a cold twenty minutes in the corral and a warm final hour. Train some long runs starting in the dark so the early alarm is routine by race week.
Is the Colfax Marathon a good Boston qualifier?
Colfax is a Boston qualifying course on paper and a poor one in practice. 2.5% of finishers ran qualifying times in 2026 and 3.6% did in 2025, and the rate has not reached 6% in any year since 2021. Altitude costs you minutes that a course with only 693 feet of climbing has no way to give back.
Is the Colfax Marathon a good first marathon?
It is a good first marathon if you live in Denver and a risky one if you do not. The profile is gentle, the field runs to a few thousand, and the 6:00 a.m. start keeps you ahead of the heat. The six hour limit is real, though, and altitude makes a first-timer's pace much harder to judge.
When should I start training for the Colfax Marathon 2027?
Race day is May 16, 2027. Counting back from that date, a 20-week build starts around December 27, 2026, a 16-week build around January 24, 2027, and a 12-week build around February 21, 2027. Already inside that window? Stride maps a plan from today to race day, whatever the runway.
How does Stride's Colfax Marathon plan work?
Download the app, pick the Colfax Marathon as your race, and answer a few questions about your recent running and your weekly schedule. Stride matches you to one of 14 marathon plans, maps every week from today to May 16, 2027, adjusts when life gets in the way, and puts you in a feed of runners training for the same race.
Choosing a training app?
A Colfax Marathon buildup is months of your life. See how Stride compares before you commit it to an app.
Find your plan.
Your race, current mileage, recent longest run, goal, and run days determine which plans rank first. Choose one and subscribe, then open every workout in Stride.