Weather Prettiness Index

The Weather Prettiness Index is a 0-100 score that predicts how willing people are to get outside based on weather conditions. It scores ~1,700 ASOS/AWOS stations across the continental United States using a weighted formula that considers temperature comfort, sunshine, precipitation, humidity, wind, visibility, and UV index.

How It Works

Each station-day is scored using a combination of absolute comfort (is 75°F and sunny?) and location-relative acclimation (how does today compare to what's normal here?).

The acclimation component is asymmetric by design — warmth tolerance is relative (85°F feels fine in Florida but hot in Maine), while cold intolerance is universal (32°F is cold for everyone, regardless of where you live). This is backed by NPS park visitation data showing that cold suppresses outdoor activity far more than heat: January park visits are roughly 1/3 of summer peaks for year-round CONUS parks.

When temperatures drop below 50°F, a cold dampener reduces the overall score — clear skies and low humidity don't matter much when it's freezing outside. Overnight lows below freezing also carry a significant penalty.

Component Weights

Temperature (30%) — Gaussian comfort curve centered at 75°F. Cold side drops faster than warm side (sigma 14 vs 15). Acclimation weight scales with temperature: 35% relative credit at 65°F+, dropping to 5% below 45°F. Overnight freeze penalty up to 25 points.
Sky / Sunshine (20%) — Cloud cover percentage with a relative bonus for sunnier-than-normal days.
Precipitation (18%) — Dry = 100, trace rain = 75, moderate rain = 40-60, heavy rain or ice = near 0.
Humidity (14%) — Dew point comfort scale. Sweet spot 50-55°F dew point = 100. Above 70°F dew point (oppressive) drops sharply.
Wind (10%) — Light breeze (3-8 mph) is ideal. Strong wind penalized, with a warm-weather breeze bonus and a cold+wind extra penalty.
Visibility (4%) — Clear views > 10 miles = 100, fog penalized.
UV Index (4%) — Moderate UV (3-5) is ideal, extreme UV penalized.

After the weighted sum, a cold dampener scales the overall score down when the high temperature is below 50°F (factor ranges from 1.0 at 50°F to 0.25 at 0°F). Severe weather events (tornado warnings, blizzards, etc.) apply additional penalties up to 50 points.

Example Scores

Calculated using the current scoring algorithm

Scenario	Score	Temp	Sky	Humidity	Wind	Precip
San Diego, Oct — 75°F, clear, light breeze	92	87	100	100	100	100
Denver, May — 72°F, sunny, breezy	89	87	94	99	85	100
Atlanta, Apr — 78°F, partly cloudy	88	89	81	93	100	100
Coastal, year-round — 82°F, clear, trade winds	82	77	99	63	85	100
Phoenix, Jun — 110°F, clear, calm	69	12	100	98	100	100
Minneapolis, Jan — 55°F, cloudy (warm spell!)	67	49	40	98	85	100
Miami, Aug — 90°F, partly cloudy, humid	54	55	67	10	95	50
Seattle, Nov — 48°F, overcast, drizzle	41	18	6	99	100	41
Chicago, Mar — 35°F, overcast, rain/snow mix	24	0	14	97	56	30
Minneapolis, Jan — 10°F, clear, windy	22	0	99	70	36	100

Note: Minneapolis at 10°F scores 22 despite clear skies and no precipitation — the cold dampener ensures that freezing temperatures override good conditions in other categories. The 55°F warm spell scores 67: warmer than normal helps via acclimation, but the cold dampener still reduces the overall score since 55°F is borderline.

Population Weighting

Station scores are aggregated to state and national levels using county-centric population weighting. Each county's population (2024 Census estimates) is split among all weather stations within 75km using inverse-distance-squared weighting. This prevents dense-station metro areas from being over-counted — 10 stations near NYC split Manhattan's population rather than each claiming all of it.

The national index reflects how many Americans are experiencing pretty weather on any given day. Total station weights sum to ~337 million, closely matching the actual US population.

Data Sources

NOAA ISD-Lite — Historical hourly observations (2018-present), the primary source for station baselines and historical scores
Open-Meteo Forecast API — 7-day forecasts including UV index and visibility
US Census Bureau — County population estimates and gazetteer coordinates for population weighting

Coverage