Race-day weather · Sunday, May 16, 2027

Colfax Marathon weather.

20 Colfax Marathon race mornings since 2006, measured hour by hour: temperature, dew point, wind, rain, and what the weather cost runners. The forecast for the 2027 race goes live here on May 10, six days out.

81 Typical score
at the start The median race morning since 2006: 45°F air + 36°F dew point at 6am, across 20 race mornings at the Centennial Airport weather station. No adjustment needed.
Start · 6am8145° air · 36° dew point
+2 hours · 8am8952° air · 37° dew point
+4 hours · 10am9760° air · 37° dew point

The Colfax Marathon course, mile by mile: the elevation, every climb, and how I’d run each stretch.

Your goal pace on a typical race morning

Built from the median race morning since 2006, averaged across the hours you’d be running. Where the weather costs time, each cell gives the adjusted finish time and the pace per mile to run instead. Six days out, the real forecast replaces it.

Goal on a cool dayAdjusted finish
2:456:18/miNo changescore 86
3:006:52/miNo changescore 86
3:157:26/miNo changescore 87
3:308:01/miNo changescore 88
3:458:35/miNo changescore 88
4:009:09/miNo changescore 88
4:3010:18/miNo changescore 90
5:0011:27/miNo changescore 90
How I’d race a typical year

Race the plan as written. This is the weather marathons are built for, and the only real risk is going out too fast because the first miles feel free. Hold goal pace through halfway and let the second half decide itself.

Race week, start to finish: how I’d run the three-week taper, what to take in during the race, how much to slow down in heat and humidity, and what the four weeks after should look like.

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Colfax Marathon weather history: every race morning since 2006

Every row in the table below is a measurement from the Centennial Airport weather station, taken nearest 6am (today’s first-wave start) and again three hours later. Start times have moved over the years, so treat 6am as a clock time, not always the gun. Across 20 race mornings:

  • A typical 6am reading is 45°F with a 36°F dew point, a combined score of 81.
  • The warmest was 2024: 57°F with a 41°F dew point at 6am, a score of 98.
  • The most humid was 2026, with a 42°F dew point.
  • The coldest was 2021, at 32°F.
  • On 0 of 20 race mornings the 6am score was above 100, enough to call for a pace adjustment. Three hours later, 6 of 20 were.
  • The windiest start was 2026: N wind at 10 mph.
  • Rain fell in the first 5 hours on 1 of 20 race mornings.
Colfax Marathon weather by year · air / dew point (°F), combined score, wind and rain
YearDateAir / dew at 6amScoreAir / dew at 9amScoreWind at 6amRain
2026May 1753° / 42°9555° / 38°93N 10 mphDry
2025May 1846° / 36°8253° / 41°94WSW 5 mphDry
2024May 1957° / 41°9867° / 43°110WSW 8 mphDry
2023May 2148° / 40°8860° / 43°103CalmDry
2022May 1549° / 29°7866° / 33°99W 7 mphDry
2021Oct 16Moved to Saturday, Oct 16 (COVID-19)32° / 16°4850° / 18°68S 6 mphDry
2020–Virtual only (COVID-19), no race morning
2019May 1939° / 35°7442° / 36°78NNE 7 mphDry
2018May 2042° / 40°8245° / 41°86ESE 5 mphDry
2017May 2138° / 32°7053° / 31°84ESE 6 mphDry
2016May 1540° / 33°7347° / 35°82WNW 3 mphDry
2015May 1743° / 29°7256° / 31°87SSE 7 mphDry
2014May 1852° / 38°9065° / 38°103SW 7 mphDry
2013May 1947° / 38°8558° / 30°88S 5 mphDry
2012May 2041° / 38°7955° / 44°99SE 3 mphDry
2011May 1535° / 34°6935° / 33°68E 8 mph0.01 in
2010May 1640° / 34°7449° / 38°87SSE 7 mphDry
2009May 1744° / 36°8064° / 33°97SSE 3 mphDry
2008May 1846° / 34°8067° / 35°102SSW 3 mphDry
2007May 2052° / 39°9165° / 40°105WSW 6 mphDry
2006May 2153° / 41°9472° / 33°105CalmDry

Readings from the Centennial Airport ASOS weather station (NOAA/FAA, via the Iowa Environmental Mesonet), the observation nearest each hour. Scores above 100 call for a pace adjustment. Rain is the total the station measured in the 5 hours after 6am. Download every hour as a CSV.

How the score works

Add the air temperature to the dew point, both in Fahrenheit. That combined score is closer to what your body feels than the temperature alone, because dew point decides whether your sweat can evaporate, and evaporating sweat is how you shed heat at race pace. The bands below are the same ones my heat pace calculator uses, and that page has the full chart and the physiology behind it.

Combined score → how much to slow down
  • 100 or lessNo pace adjustment
  • 101 – 1100% to 0.5% slower
  • 111 – 1200.5% to 1% slower
  • 121 – 1301% to 2% slower
  • 131 – 1402% to 3% slower
  • 141 – 1503% to 4.5% slower
  • 151 – 1604.5% to 6% slower
  • 161 – 1706% to 8% slower
  • 171 – 1808% to 10% slower
  • Above 180Hard running is not recommended

The bands are a coach's rule of thumb, not a lab measurement. Treat each range as a starting point and let effort make the final call.

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Other race-day weather pages

Twin Cities MarathonSunday, October 4, 202695Race day at the startNo adjustment needed Chicago MarathonSunday, October 11, 2026113Race day at the startSlight penalty: 0.5% to 1% slower Columbus MarathonSunday, October 18, 202664Forecast at the startNo adjustment needed Detroit MarathonSunday, October 18, 202672Forecast at the startNo adjustment needed Marine Corps MarathonSunday, October 25, 202694Typical startNo adjustment needed NYC MarathonSunday, November 1, 202683Typical startNo adjustment needed Philadelphia MarathonSunday, November 22, 202673Typical startNo adjustment needed California International MarathonSunday, December 6, 202683Typical startNo adjustment needed Honolulu MarathonSunday, December 13, 2026136Typical startReal penalty: 2% to 3% slower Houston MarathonSunday, January 17, 202784Typical startNo adjustment needed LA MarathonSunday, March 7, 202799Typical startNo adjustment needed Atlanta MarathonSunday, March 7, 202797Typical startNo adjustment needed Jersey City MarathonSunday, April 18, 202791Typical startNo adjustment needed Boston MarathonMonday, April 19, 202784Typical startNo adjustment needed Rock 'n' Roll Nashville MarathonSaturday, April 24, 2027111Typical startSlight penalty: 0.5% to 1% slower Eugene MarathonSunday, April 25, 202789Typical startNo adjustment needed Big Sur MarathonSunday, April 25, 202796Typical startNo adjustment needed Flying Pig MarathonSunday, May 2, 2027102Typical startBarely a penalty: 0% to 0.5% slower Pittsburgh MarathonSunday, May 2, 202799Typical startNo adjustment needed OC MarathonSunday, May 2, 2027110Typical startBarely a penalty: 0% to 0.5% slower Rock 'n' Roll San Diego MarathonSunday, June 6, 2027119Typical startSlight penalty: 0.5% to 1% slower Grandma's MarathonSaturday, June 19, 2027112Typical startSlight penalty: 0.5% to 1% slower San Francisco MarathonSunday, July 25, 2027109Typical startBarely a penalty: 0% to 0.5% slower

Course guides, mile by mile: Twin Cities Marathon, Chicago Marathon, Columbus Marathon, Detroit Marathon, Marine Corps Marathon, NYC Marathon, Philadelphia Marathon, California International Marathon, Honolulu Marathon, Houston Marathon, LA Marathon, Jersey City Marathon, Boston Marathon, Rock 'n' Roll Nashville Marathon, Eugene Marathon, Big Sur Marathon, Flying Pig Marathon, Pittsburgh Marathon, OC Marathon, Rock 'n' Roll San Diego Marathon, Grandma's Marathon, San Francisco Marathon. All race-day weather pages.

RunFitCoach is not affiliated with the Denver Colfax Marathon or its organizers. Observations from the Centennial Airport ASOS station (NOAA/FAA) via the Iowa Environmental Mesonet. Data updated Saturday, October 17, 2026.

Heat is one variable. I plan for all of them.

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