See the pace the weather allowed.

The timeline stress bar is a 0-100 snapshot of how taxing the weather was at that moment. It rises when temperature, dew point, wind, and solar load rise.

Current formula:

stress =
max(0, tempF - 52) * 1.4 +
max(0, dewPointF - 50) * 2.1 +
max(0, windMph - 6) * 1.3 +
solarWm2 / 35

Then clamp to 0-100.

Dew point has the biggest effect because humid air makes it harder to cool yourself through sweat evaporation.

Weather Grade is a 0-100 composite score showing how favorable the conditions were for endurance performance.

Weather Grade =
Temperature score * 30% +
Dew point score * 35% +
Wind score * 15% +
Solar score * 10% +
Rain score * 10%

Higher is better. Cool, dry, calm conditions tend to grade highest.

Weather Score is a simplified 1-10 label derived from Weather Grade.

Weather Score = round(Weather Grade / 10)
Clamp to 1-10

That score then maps to labels like Perfect, Good, Challenging, or Extreme.

PaceWeather also pairs each score with a face emoji so the effort reads at a glance, from 😁 in ideal weather down to 😵 in the most punishing conditions.

This emoji scale is about overall feel. It reflects the 1-10 Weather Score, not the exact number of seconds lost.

Weather Cost estimates seconds per mile lost due to environmental conditions.

Heat cost = max(0, tempF - 60) * 0.35
Humidity cost = max(0, dewPointF - 45) * 1.2
Wind cost = max(0, windMph - 8) * 0.45
Rain cost = max(0, rainMm - 0.2) * 2.5
Solar cost = max(0, solarWm2 - 250) / 60

Weather Cost = sum of the above

Right now this is a rules-based estimate, not a personalized athlete model.

Weather Cost uses a separate severity emoji scale from Weather Score because it represents pace loss, not overall feel: 🟢 0-5, 🟡 6-15, 🟠 16-30, 🔴 31-45, and 🥵 46+ seconds per mile.

These are early personalized scores built from your own weather-ready history. They are not lab measurements. They simply ask: “How far does your actual pace drift away from your own weather-normalized baseline when conditions turn hot or humid?”

baseline pace =
average Perfect Weather Pace from cool/dry runs

If there are not enough cool/dry runs:
baseline pace =
average Perfect Weather Pace from all weather-ready runs

tolerance drag =
average actual pace in hot or humid runs - baseline pace

tolerance score =
100 - (tolerance drag * 1.3)

Then clamp to 0-100.

Higher is better. A higher score means your hot or humid runs stay closer to your own weather-normalized baseline. A lower score means your pace fades farther from that baseline in those conditions.

This is intentionally simple and transparent. It is a first-pass athlete profile, not a finished physiology model.

The monthly tolerance trend table uses the same score month by month. That makes it useful for spotting direction over time, but it should still be read as a rough training-history signal, not a formal acclimation study.

The rolling acclimation cards go one step further. They compare the most recent 30-day window in your synced history against the 30 days before that. If the recent window scores higher, PaceWeather marks that as improving acclimation. If it drops, the app flags that your recent heat or humidity readiness may be cooling off.

Terrain Effect is a separate estimate of how much climbing likely slowed the run. It is not weather. It is meant to show the elevation side of the effort when you want that context in the summary.

If GAP is available, PaceWeather uses the difference between actual pace and GAP as the terrain effect.

If GAP exists:
Terrain Effect = max(0, actual pace - GAP)

If GAP is not available, PaceWeather falls back to a simple elevation-gain estimate based on feet climbed per mile.

If GAP is missing:
gainPerMile = elevationGainFeet / distanceMiles
Terrain Effect = max(0, gainPerMile - 50) * 0.18

This fallback is a heuristic, so it should be treated as a directional estimate rather than an exact terrain model.

PaceWeather now supports two pace views so you can decide whether elevation should be part of the normalization.

Perfect Weather Pace removes weather impact only. It starts from your actual pace and subtracts Weather Cost.

Perfect Weather Pace =
actual pace - Weather Cost

Perfect Pace removes weather impact and also accounts for terrain by using GAP when available, or by subtracting the estimated Terrain Effect when GAP is missing.

Perfect Pace =
GAP - Weather Cost

If GAP is missing:
Perfect Pace =
actual pace - Terrain Effect - Weather Cost

If you want a cleaner answer to “what would this have looked like in better weather on the same route?”, choose Perfect Weather Pace. If you want a pace that also smooths out elevation impact, choose Perfect Pace.

PaceWeather marks these pace metrics with 🎯 to show they are target or normalized pace values rather than raw activity pace.

Estimated Time Lost turns per-mile weather cost into total run time.

Estimated Time Lost =
distanceMiles * weatherCostSecondsPerMile

Primary Limiter is whichever Weather Cost component contributed the most pace loss on that run: heat, humidity, wind, rain, or solar load.

Temp: Air temperature near the route.

Hum: Relative humidity.

Dew Pt: Dew point temperature, a better proxy for muggy air.

Solar: Solar radiation in watts per square meter, which acts like sun load.

Clouds: Cloud cover percentage.

The timeline samples the run every 30 minutes using archived hourly weather. Between each hour, PaceWeather interpolates the values so half-hour points behave more naturally.

Timeline coverage uses the longest trustworthy activity duration available: elapsed time first, then stream duration, then moving time.

PaceWeather currently pulls historical weather from the Open-Meteo Archive API.

We use Strava to provide the activity start time, timezone, and route coordinates. Then we request archived hourly weather for that location and date range.

Source: Open-Meteo archive-api.open-meteo.com

Requested hourly fields:
- temperature_2m
- relative_humidity_2m
- dew_point_2m
- precipitation
- cloud_cover
- wind_speed_10m
- shortwave_radiation

For the timeline, PaceWeather samples across the activity window and interpolates between hourly weather points so half-hour entries feel smoother than a simple hour-by-hour snap.

This means the weather is route-area historical weather, not a body-worn sensor or exact microclimate reading at every step.