Races›Ultra 100K

Lake Sonoma

Lake Sonoma is Apr 10, 2027 in Geyserville area. Plan for humid air, then build your free hour-by-hour plan.

RunningUltra 100K (62.1 mi)Registration Open
LocationGeyserville area, California, US
Date
April 10, 2027
Build Your Fueling PlanOfficial website
Race Location38.72°, -123.00°
View larger map

Race-Day Conditions

Moderate Heat Risk
Temperature
74°F

57–81°F range

Humidity
68%

48–77% range

5-year average via Open-Meteo. 80% of race days fall within the range shown. Updated Nov 6, 2026.

!

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 Ultra 100K Nutrition Plan

Based on a 155 lb runner finishing in ~14 hours. Your plan will differ based on body weight, experience, and conditions.

HourCarbsFluidSodiumExample
Hours 1–3180g57oz1400mgGels + sports drink
Hours 4–7240g75oz2000mgMix of gels, chews, real food
Hours 8–10150g53oz1500mgBroth, PB sandwich, gels
Hours 11–14180g62oz1600mgWhatever stays down + cola
Total750g247oz6500mg

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

What to Expect at Lake Sonoma

Lake Sonoma is a 100K ultra held in Geyserville area, California, US. Based on 5 years of historical weather data, athletes can expect median race-day temperatures around 74°F.

Temperatures at Lake Sonoma typically range from 57°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. Humidity is also a factor here, with levels reaching 77% on warmer days. High humidity impairs sweat evaporation — your body's primary cooling mechanism — so perceived effort rises even when temperatures look manageable on paper.

Ultra-distance racing demands a flexible nutrition strategy. Gut absorption efficiency declines over many hours, so plan for variety — alternating between gels, chews, real food, and liquids helps prevent flavor fatigue and GI rebellion. Many ultra runners find that what works at hour 3 is intolerable by hour 10. Build your plan with options, not rigid prescriptions.

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.

See something wrong? Let us know and we'll fix it.

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.

Ready to fuel Lake Sonoma?

Get a personalized, hour-by-hour fueling blueprint based on your body, this race's course, and historical weather data. Free, no account needed.

Build Your Plan

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 Ultra 100K.
What is the typical race-day weather?
Based on 5 years of historical data, race-day temperatures at Geyserville area, California typically range from 57°F to 81°F (median 74°F). Humidity ranges from 48% to 77%.
How much water should I drink?
Fluid needs vary based on your sweat rate, body weight, and race-day temperature. A typical range for moderate days is about 500-800 ml/hr, but hotter conditions at Geyserville area, California 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 Ultra 100K 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: curatedView sourceVerified: Nov 4, 2026Confidence: 80%