Boulderthon Marathon

Boulder, CO, USA · September 27, 2026

51°·74° high·Light·Dry

Weather

Race Day Weather

51°at start

77° high

Light

Dry

Cool start, warming trend

Runners will face a temperature rise from 51°F at the start to a warm 76°F by the finish. Winds will be light, coming from the S at 7 mph, with gusts up to 16 mph. With humidity at a comfortable 37%, pacing adjustments may be needed as temperatures increase, particularly after the halfway mark.

Race day forecast available in 60 days

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Distance: 26.2mi

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Race Info

Named among the Best Fall Marathons by Runner's World, #5 Best Half Marathon in the US by Active, as well as #1 Best in Colorado and one of the "Most Beautiful Marathons in the World" by HalfMarathons.Net, Boulderthon drew over 6,000 runners from all 50 states and 18 countries in 2023, and has doubled in size every year since its inception. Source

Website

Course Map

FAQ

When is the 2026 Boulderthon Marathon?

The 2026 Boulderthon Marathon will be held on Sunday September 27, 2026.

Is the Boulderthon Marathon a Boston Marathon Qualifier?

Yes, the Boulderthon Marathon is an official Boston Marathon qualifier.

What is the time limit for the Boulderthon Marathon?

The time limit for the Boulderthon Marathon is 6.5 hours.

What will the weather be like for the 2026 Boulderthon Marathon?

The forecast calls for a high of 79°F and a low of 50°F with a 4% chance of rain.

Historical Weather

Based on 5 years of data

Avg Temp

75°F

L:50° H:75°

RunScore

Conditions

Rain Freq

0 of 5 yrs

Wind4mph

Dew35°F

Temperature History

Range of temperatures during race hours for each year.

Detailed History

Year	Low / High	Rain	Dew Point
2025 Boulderthon Marathon Partly cloudy throughout the day. 2025	54°/77°	-	46°
2024 Boulderthon Marathon Clear conditions throughout the day. 2024	60°/84°	-	41°
2023 Boulderthon Marathon Clear conditions throughout the day. 2023	46°/77°	-	30°
2022 Boulderthon Marathon Clear conditions throughout the day. 2022	43°/72°	-	34°
2021 Boulderthon Marathon Clear conditions throughout the day. 2021	45°/66°	-	29°

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