Training
Long Run Weather Adjustments
How to adapt to heat, cold, humidity, and everything in between
Weather doesn't care about your training plan. Heat slows you down, cold requires extra gear, and humidity makes everything harder. The runners who train well year-round are the ones who know how to adjust-not just push through.
Plan Your Long Run Fueling
Hot weather means more hydration. Calculate exactly how much you need.
Fueling Calculator →Running in Heat
Heat is the most significant weather factor for most runners. Your body has to work harder to cool itself, diverting blood to the skin that would otherwise go to working muscles.
How Much to Slow Down
Heat Pace Adjustments
- 55-65°F: Optimal-no adjustment needed
- 65-75°F: Slow 20-30 sec/mile
- 75-85°F: Slow 40-60 sec/mile
- 85°F+: Consider shortening the run or switching to effort-based
These are guidelines, not rules. Some runners handle heat better than others. Pay attention to your body-if you're overheating, slow down regardless of what the chart says.
Heat Strategies
- Start early: The coolest part of the day is usually just before sunrise
- Seek shade: Route along tree-covered paths when possible
- Pre-cool: Cold water or ice before the run can help
- Plan water stops: More frequent hydration in heat
- Wear light colors: They reflect heat; dark absorbs it
- Run by effort: Let pace be what it is; focus on sustainable effort
Heat Adaptation
Good news: your body adapts to heat over 10-14 days of exposure. Plasma volume increases, sweat rate improves, and perceived effort decreases. If you're training for a hot race, some heat exposure is beneficial. But don't overdo it-heat training carries real risk.
Running in Humidity
Humidity is insidious because it impairs cooling. Sweat can't evaporate efficiently when the air is already saturated with moisture, so your primary cooling mechanism fails.
Heat Index Matters
Check the heat index, not just temperature. 75°F with 90% humidity can feel like 85°F. Use the heat index to guide your pace and distance decisions.
Humidity Impact
- Below 40% humidity: Minimal impact on cooling
- 40-60% humidity: Moderate impact; some pace adjustment
- 60-80% humidity: Significant impact; expect slower times
- Above 80% humidity: Major impact; be very conservative
High humidity often requires more adjustment than dry heat at the same temperature. A 70°F day with 95% humidity can be harder than 80°F with 30% humidity.
Running in Cold
Cold weather is generally easier to manage than heat-you can always add layers. The risks are different: hypothermia, frostbite, and slick surfaces.
Dressing for Cold
The classic advice: dress for 15-20°F warmer than actual temperature. You'll be cold for the first 10 minutes, then comfortable.
Cold Weather Layering
- Base layer: Moisture-wicking fabric (never cotton)
- Mid layer: Insulation (fleece, light down)
- Outer layer: Wind and water protection
- Extremities: Gloves, hat/headband, face covering in extreme cold
Temperature Guidelines
- 40-50°F: Long sleeves, maybe light gloves
- 30-40°F: Tights, gloves, hat, layers on top
- 20-30°F: Full cold weather gear, consider face protection
- Below 20°F: Exposed skin risks frostbite; full coverage essential
- Below 0°F: Consider treadmill or significant route modifications
Cold Weather Considerations
- Warm up indoors: Dynamic stretching before heading out
- Wind chill: Plan your route to finish with wind at your back
- Footing: Ice and snow require slower pace and shorter strides
- Hydration: You still sweat in cold; don't skip fluids
- Be seen: Winter means less daylight; wear reflective gear
Running in Wind
Wind increases energy cost-running into a 15 mph headwind can feel like running uphill. The effect is even more pronounced during long runs when fatigue accumulates.
Wind Strategies
- Out and back: Start into the wind, return with it
- Loop routes: Wind direction varies; you'll have some relief
- Draft: Running with others reduces wind impact
- Lower expectations: Wind costs time; adjust pace accordingly
A tailwind helps, but not as much as a headwind hurts. Don't expect to "make up time" on the return leg-run by effort throughout.
Running in Rain
Light rain is often ideal running weather-natural cooling without excessive heat. Heavy rain presents challenges but is usually manageable.
Rain Strategies
- Wear a brim: Baseball cap keeps rain out of your eyes
- Moisture-wicking fabrics: Cotton becomes heavy and causes chafing
- Anti-chafe products: Wet conditions increase friction
- Waterproof phone storage: Protect electronics
- Watch footing: Wet surfaces, especially leaves and painted lines, are slick
When Rain Becomes a Problem
Light rain? Go run. Thunderstorms with lightning? Stay inside. If you hear thunder, you're within striking distance-get off exposed routes immediately.
When to Modify or Skip
Sometimes the smart choice is to adjust or postpone. One modified long run won't hurt your training. An injury or health emergency will.
When to Stay Inside
- Lightning in the area
- Heat index above 100°F
- Wind chill below -20°F
- Ice-covered roads without alternatives
- Air quality warnings
- Feeling unwell (weather stress + illness = trouble)
Alternatives
If conditions are truly dangerous:
- Treadmill: Not ideal, but safe and controlled
- Move the run: Can you go tomorrow instead?
- Split it: Two shorter runs can replace one long one in emergencies
- Accept the miss: One skipped long run doesn't ruin a training cycle
The Bottom Line
Weather is a variable, not an excuse. Most conditions are manageable with proper preparation and realistic expectations. But "tough it out" has limits-know when conditions cross from challenging to dangerous.
The goal is consistent training over months and years. One smart decision to modify a run protects dozens of future runs.
Plan Your Long Run
Get a sustainable long run recommendation based on your weekly mileage.
Long Run Calculator →Frequently Asked Questions
How much should I slow down in hot weather?
A common guideline is to slow down 20-30 seconds per mile for every 10°F above 55°F. At 75°F, that's 40-60 seconds per mile slower. At 85°F+, consider reducing distance or running by effort rather than pace. Heat affects everyone-elite runners slow down in hot races too.
Should I skip my long run in bad weather?
It depends on the conditions. Light rain, moderate cold, or mild heat are fine with proper preparation. Dangerous conditions-lightning, extreme heat (heat index above 100°F), icy roads, or severe wind chill-warrant postponement. One skipped long run won't ruin your training; an injury will.
How does humidity affect running?
Humidity impairs your body's ability to cool through sweating. Even at moderate temperatures (70°F), high humidity can feel much harder. Use the heat index rather than temperature alone to gauge conditions. High humidity often requires more pace adjustment than dry heat at the same temperature.
How do I dress for cold weather long runs?
Dress for 15-20°F warmer than the actual temperature-you'll heat up once running. Layer with moisture-wicking base layers, insulating mid-layers, and wind-blocking outer layers. Protect extremities (hands, ears, face) as they lose heat fastest. Adjust layers throughout if needed.