Race-day weather · Sunday, October 18, 2026

Detroit Marathon weather.

The forecast for Sunday, October 18, 2026: 40°F with a 33°F dew point at the 7am start, a combined score of 73. By 10am it reaches 83. Sunny at the start with a SW wind at 8 mph. For a 3:30 runner in the first wave, that needs no pace adjustment. Here is every goal time and pace adjusted, and how I’d race it.

73 Combined score
at the start Forecast: 40°F air + 33°F dew point at the 7am start. No adjustment needed at the start. National Weather Service forecast issued Thu Oct 15, 3:49pm EDT.
Start · 7am7340° air · 33° dew pointSunny · SW wind 8 mph
+2 hours · 9am7844° air · 34° dew pointSunny · SW wind 9 mph
+4 hours · 11am8851° air · 37° dew pointSunny · SW wind 10 mph

Your goal pace, adjusted for the forecast

Find your cool-weather goal on the left. Each cell gives the adjusted finish time and the pace per mile to run instead, averaged across the hours you’ll actually be running.

Goal on a cool dayAdjusted finish
2:456:18/miNo changescore 77
3:006:52/miNo changescore 77
3:157:26/miNo changescore 78
3:308:01/miNo changescore 79
3:458:35/miNo changescore 79
4:009:09/miNo changescore 79
4:3010:18/miNo changescore 81
5:0011:27/miNo changescore 81
How I’d race it

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.

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Detroit Marathon weather history: every race morning since 2000

Every row in the table below is a measurement from the Detroit Metro Airport weather station, taken nearest 7am (today’s first-wave start) and again three hours later. Start times have moved over the years, so treat 7am as a clock time, not always the gun. Across 25 race mornings:

  • A typical 7am reading is 45°F with a 39°F dew point, a combined score of 84.
  • The warmest was 2017: 70°F with a 66°F dew point at 7am, a score of 136.
  • The most humid was 2017, with a 66°F dew point.
  • The coldest was 2009, at 30°F.
  • On 6 of 25 race mornings the 7am score was above 100, enough to call for a pace adjustment. Three hours later, 8 of 25 were.
  • The windiest start was 2017: SSW wind at 18 mph.
  • Rain fell in the first 5 hours on 4 of 25 race mornings (1 more saw only a trace).
Detroit Marathon weather by year · air / dew point (°F), combined score, wind and rain
YearDateAir / dew at 7amScoreAir / dew at 10amScoreWind at 7amRain
2025Oct 1965° / 63°12865° / 62°127S 17 mphgusts 260.06 in
2024Oct 2043° / 37°8052° / 42°94SSW 6 mphDry
2023Oct 1545° / 41°8650° / 43°93NW 7 mphDry
2022Oct 1640° / 32°7247° / 35°82SW 7 mphDry
2021Oct 1746° / 39°8549° / 41°90W 9 mphDry
2020–Virtual only (COVID-19), no race morning
2019Oct 2047° / 45°9252° / 47°99CalmDry
2018Oct 2137° / 26°6338° / 26°64NW 13 mphDry
2017Oct 1570° / 66°13674° / 66°140SSW 18 mphLight rain
2016Oct 1664° / 59°12369° / 60°129SSW 13 mph0.08 in
2015Oct 1836° / 27°6339° / 28°67W 6 mphDry
2014Oct 1933° / 29°6239° / 31°70NW 5 mphDry
2013Oct 2039° / 36°7545° / 39°84S 8 mphDry
2012Oct 2139° / 37°7647° / 42°89SSW 5 mphDry
2011Oct 1652° / 39°9151° / 41°92S 8 mphLight rain
2010Oct 1748° / 42°9050° / 43°93NNW 7 mphDry
2009Oct 1830° / 25°5540° / 29°69NW 6 mphDry
2008Oct 1936° / 31°6744° / 36°80CalmDry
2007Oct 2154° / 43°9764° / 44°108SSW 9 mphDry
2006Oct 2938° / 24°6245° / 25°70W 13 mphDry
2005Oct 2340° / 36°7644° / 38°82NNE 6 mphDry
2004Oct 2453° / 49°10255° / 50°105W 6 mphDry
2003Oct 534° / 31°6543° / 35°78CalmDry
2002Oct 646° / 44°9057° / 51°108CalmDry
2001Oct 2153° / 52°10561° / 55°116SSW 6 mphDry
2000Oct 1555° / 52°10760° / 53°113S 7 mphTrace

Readings from the Detroit Metro 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 7am. 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, 202666Forecast 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 Boston MarathonMonday, April 19, 202784Typical startNo adjustment needed Grandma's MarathonSaturday, June 19, 2027112Typical startSlight penalty: 0.5% to 1% slower

All race-day weather pages

RunFitCoach is not affiliated with the Detroit Free Press Marathon or its organizers. Forecasts from the National Weather Service. Observations from the Detroit Metro Airport ASOS station (NOAA/FAA) via the Iowa Environmental Mesonet. Data updated Thursday, October 15, 2026.

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