Race-day weather · Monday, April 19, 2027

Boston Marathon weather.

26 Boston Marathon race mornings since 2000, measured hour by hour: temperature, dew point, and what the weather cost runners. The forecast for the 2027 race goes live here on Apr 13, six days out.

84 Typical score
at the start The median race morning since 2000: 49°F air + 36°F dew point at 10am, across 26 race mornings at the Boston Logan weather station. No adjustment needed.
Start · 10am8449° air · 36° dew point
+2 hours · 12pm8650° air · 36° dew point
+4 hours · 2pm8952° air · 37° dew point

Your goal time on a typical race morning

Built from the median race morning since 2000, averaged across the hours you’d be running. Six days out, the real forecast replaces it.

Goal on a cool dayStarting 10amStarting 11:21am
2:45No changescore 85No changescore 87
3:00No changescore 85No changescore 87
3:15No changescore 86No changescore 87
3:30No changescore 86No changescore 87
3:45No changescore 86No changescore 87
4:00No changescore 86No changescore 87
4:30No changescore 86No changescore 87
5:00No changescore 86No changescore 88
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.

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Boston Marathon weather on race morning since 2000

Every row in the table below is a measurement from the Boston Logan weather station, taken nearest 10am (today’s first-wave start) and again three hours later. Start times have moved over the years, so treat 10am as a clock time, not always the gun. Across 26 race mornings:

  • A typical 10am reading is 49°F with a 36°F dew point, a combined score of 84.
  • The warmest was 2012: 74°F with a 58°F dew point at 10am, a score of 132.
  • The most humid was 2021, with a 59°F dew point.
  • The coldest was 2018, at 40°F.
  • On 7 of 26 race mornings the 10am score was above 100, enough to call for a pace adjustment. Three hours later, 6 of 26 were.
Boston Marathon race mornings · air / dew point (°F) and combined score
YearDateAir / dew at 10amScoreAir / dew at 1pmScore
2026Apr 2045° / 29°7450° / 26°76
2025Apr 2149° / 25°7450° / 28°78
2024Apr 1558° / 48°10667° / 48°115
2023Apr 1748° / 48°9648° / 48°96
2022Apr 1848° / 26°7449° / 31°80
2021Oct 1165° / 59°12468° / 60°128
2020–Virtual only (COVID-19), no race morning
2019Apr 1556° / 53°10963° / 55°118
2018Apr 1640° / 40°8043° / 43°86
2017Apr 1770° / 46°11673° / 34°107
2016Apr 1866° / 31°9757° / 34°91
2015Apr 2042° / 40°8243° / 40°83
2014Apr 2152° / 27°7955° / 35°90
2013Apr 1548° / 30°7848° / 34°82
2012Apr 1674° / 58°13277° / 57°134
2011Apr 1849° / 25°7457° / 25°82
2010Apr 1950° / 32°8253° / 33°86
2009Apr 2046° / 36°8247° / 36°83
2008Apr 2148° / 43°9151° / 44°95
2007Apr 1647° / 46°9348° / 39°87
2006Apr 1748° / 34°8247° / 34°81
2005Apr 1863° / 26°8962° / 29°91
2004Apr 1963° / 50°11378° / 50°128
2003Apr 2148° / 35°8350° / 35°85
2002Apr 1552° / 51°10351° / 49°100
2001Apr 1646° / 31°7745° / 36°81
2000Apr 1743° / 29°7241° / 29°70

Readings from the Boston Logan ASOS weather station (NOAA/FAA, via the Iowa Environmental Mesonet), the observation nearest each hour. Scores above 100 call for a pace adjustment. 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.

Want the next one built around you?

A forecast adjusts a pace. It doesn't know your training, how you handle heat, or how your last long run went. I write every plan by hand and set race-week pacing with each athlete. It starts with a free 20-minute call.

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Other race-day weather pages

NYC MarathonSunday, November 1, 202683Typical startNo adjustment needed Chicago MarathonSunday, October 11, 2026113Race day at the startSlight penalty: 0.5% to 1% slower Philadelphia MarathonSunday, November 22, 202673Typical startNo adjustment needed California International MarathonSunday, December 6, 202683Typical startNo adjustment needed

All race-day weather pages

RunFitCoach is not affiliated with the Boston Marathon or its organizers. Observations from the Boston Logan ASOS station (NOAA/FAA) via the Iowa Environmental Mesonet. Data updated Tuesday, October 13, 2026.

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