Weather match
Past race mornings like your forecast, and how finishes at your pace held up.
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This forecast: low risk on the race-flag heat-stress scale.
Four published estimates: 0.1% to 1.6% slower
- Relative humidity
- 73%
- Wet-bulb
- 58°F
- Shade WBGT ≈
- 60°F
- ACSM race flag
- GreenWBGT below 64°F: low risk, not none
Top finishers, seven marathonsPublished study
0.6–1.6%≈ 1:26–3:50 min on 4:00:00
Top-three finishers in seven marathons ran 3.3% (men) and 3.8% (women) off course records at a WBGT of 59–68°F, against 1.7% and 3.2% at 41–50°F. Places 25 to 300 slowed more as WBGT rose.
WBGT Men Women 41–50°F 1.7% 3.2% 50–59°F 2.5% 3.2% 59–68°F (your conditions) 3.3% 3.8% 68–77°F 4.5% 5.4% Elite marathon finalistsPublished study
0.1–0.2%≈ 0:14–0:28 min on 4:00:00
Your shade WBGT is 0.9°F above 59°F. Elite marathon finalists ran about 0.11% per °F slower above it; across all the study’s endurance events, about 0.22% per °F.
Temperature + dew point tableRule of thumb
0.5–1%≈ 1:12–2:24 min on 4:00:00
Temperature plus dew point is 64 + 55 = 119°F. Its 111–120 band suggests running 0.5–1% slower.
Dew-point bandsRule of thumb
1%≈ 2:24 min on 4:00:00
Dew point 55°F. The 55 to under 60°F band suggests about 1% slower.
Boston finishers, 1972–2018Published study
Boston 1972–2018: across all finishers, times were about 1 min 47 s slower for each 1.8°F (1°C) rise in average air temperature.
These methods disagree several-fold for the same weather. For this forecast they run from 0.1% to 1.6%.