Races›Marathon

Boise River Marathon

Race-specific weather data and nutrition strategy for Boise River Marathon in Eagle, ID, US.

RunningMarathon (26.2 mi)Registration Open
LocationEagle, ID, US
Date
May 2, 2026
Register on RunSignUpBuild Your Fueling PlanOfficial website
Race Location43.70°, -116.35°
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Race-Day Conditions

Moderate Heat Risk
Temperature
67°F

55–81°F range

Humidity
44%

33–65% range

5-year average via Open-Meteo. 80% of race days fall within the range shown. Updated Mar 30, 2026.

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Moderate heat risk

Temperatures may reach 81°F. Plan for 10-15% higher sweat rates than cool conditions. Ensure adequate sodium intake (600-900 mg/hr) and consider pre-cooling strategies.

Sample Marathon Nutrition Plan

Based on a 155 lb runner finishing in ~4 hours. Your plan will differ based on body weight, experience, and conditions.

HourCarbsFluidSodiumExample
Hour 150g18oz400mg1 gel + sports drink
Hour 270g20oz500mg2 gels + water
Hour 370g20oz500mg1 gel + 4 chews
Hour 450g15oz400mg1 gel + sports drink
Total240g73oz1800mg

These are general estimates. Get your personalized plan for this race →

What to Expect at Boise River Marathon

Boise River Marathon is a Marathon (26.2 mi) marathon held in Eagle, ID, US. Based on 5 years of historical weather data, athletes can expect median race-day temperatures around 67°F.

Temperatures at Boise River Marathon typically range from 55°F to 81°F. The upper end of that range crosses into moderate heat risk. While not extreme, sweat rates will be elevated and athletes who under-fuel on sodium or fluids may feel it in the later miles. A dialed-in hydration plan makes a real difference here.

Marathon fueling is about precision. Current sports science supports 60–90g of carbohydrates per hour for events over 2.5 hours, with experienced athletes pushing up to 120g/hr using glucose-fructose combinations. Start conservative in the first hour (around 70% of target) and build to full intake by hour two. Given the heat potential at this race, sodium intake of 600–1000mg per hour becomes critical to offset sweat losses.

We do our best to keep race details accurate and up to date, but things can change and occasionally we simply get something wrong.

Always check the official website for the most complete and current information.

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Fueling and hydration suggestions are based on published sports science research including ACSM position stands, ISSN guidelines, and peer-reviewed work by Jeukendrup, Sawka, and others. This is not medical or dietary advice — individual needs vary. Always test your nutrition strategy in training before race day.

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Frequently Asked Questions

What should I eat during the race?
Your nutrition plan depends on your body weight, experience level, and race-day conditions. Use our free calculator to get a personalized, hour-by-hour fueling plan with specific carb, fluid, and sodium targets for this Marathon.
What is the typical race-day weather?
Based on 5 years of historical data, race-day temperatures at Eagle, ID typically range from 55°F to 81°F (median 67°F). Humidity ranges from 33% to 65%.
How much water should I drink?
Fluid needs vary based on your sweat rate, body weight, and race-day temperature. A typical range is 400-800 mL per hour, but hotter conditions at Eagle, ID may require more. Our calculator provides personalized fluid targets adjusted for the expected weather.
How many calories do I need?
Rather than replacing all calories burned, focus on carbohydrate intake — the primary fuel for endurance performance. Target 30-50% of caloric expenditure through carbs. Our calculator computes the exact hourly targets based on your Marathon pace and body weight.
When should I start fueling?
Begin fueling within the first 30-45 minutes. Start at about 70% of your target intake and ramp up to full by hour 2. This gives your gut time to adjust. Starting too late makes it nearly impossible to catch up on carbs and fluids.
Source: runsignup_apiView sourceVerified: Mar 30, 2026Confidence: 95%