Data Methodology

Data Source

All data comes from the NOAA 1991–2020 U.S. Climate Normals - the official 30-year climatological averages published by the National Oceanic and Atmospheric Administration. This is the authoritative U.S. climate dataset, updated every decade.

Data Vintage

The current dataset covers the 1991–2020 period - 30 years of climate observations averaged to produce stable normals. NOAA recalculates climate normals every 10 years. The next update is expected around 2031 when the 2001–2030 period normals will be published.

Station Network

PlainClimate covers 15,492 weather stations across all 50 states, organized under 6,861 station-mapped locations. The labels include municipalities, Census-designated places, airports, facilities, and other station names; they are not all cities. Station types include:

• USW stations - Airport and first-order weather stations with the most complete records
• USC stations - Cooperative Observer Program stations operated by volunteers
• US1 stations - Community Collaborative Rain, Hail and Snow Network
• USS stations - Snow Telemetry (SNOTEL) stations in mountain regions

Variables Covered

• Monthly and annual average, minimum, and maximum temperatures (°F)
• Monthly precipitation totals (inches)
• Monthly snowfall and snow depth (inches)
• Heating and cooling degree days
• Humidity and dew point (where available)
• Wind speed (where available)
• Growing season length and frost dates (where available)

These variables represent the core climate characteristics that matter most for residential planning, agriculture, construction, and public health. Together they paint a comprehensive picture of what typical weather conditions look like in any given location across the United States.

Comfort Score Methodology

The Comfort Score (1-100) shown on eligible station-mapped location pages is a PlainClimate-computed index, not a NOAA figure - it summarizes the primary station's long-run climate using four weighted components derived from the same NOAA Climate Normals values shown elsewhere on the site:

• Temperature mildness (up to 40 points) - highest when the annual average temperature falls between 60-75°F, tapering down the further it sits outside that range.
• Precipitation (up to 30 points) - highest for 20-50 inches of annual rainfall, tapering down for drier or wetter climates.
• Snowfall (up to 15 points) - highest for under 5 inches of annual snow, decreasing as snowfall increases.
• Growing season length (up to 15 points) - highest for a frost-free season longer than 300 days, decreasing for shorter seasons.

Temperature is required for a Comfort Score to exist at all. Of the other three components, a city needs real NOAA data for at least two of the three (precipitation, snowfall, growing season) - if fewer are available, we show "Data not available" rather than compute a score, the same policy used everywhere else on the site. When a city has two or three of these components but not all four, the missing one is dropped entirely (not estimated or padded with a placeholder value) and the score is rescaled proportionally across only the components that are actually known, so scores stay comparable across cities with different data completeness. It is a transparent, rules-based index reflecting one reasonable definition of climate mildness - not an official NOAA product, not a prediction, and not the only valid way to rank climates. Two cities with different underlying temperature/precipitation/snowfall profiles can land on the identical score, which explains why occasional ties appear in city rankings.

Climate Living Index Methodology

The Climate Living Index is a separate PlainClimate-derived 0–100 score with an A–F grade. It does not replace the established Comfort Score used in rankings. It combines six measures from three NOAA U.S. Climate Normals products: annual/seasonal, daily multivariate, and hourly normals.

• Annual temperature balance (25%) - distance from a 67.5°F annual mean; lower is better.
• Precipitation balance (15%) - distance from 35 annual inches; lower is better.
• Snowfall burden (10%) - annual snowfall; lower is better.
• Frost-free season (10%) - days between NOAA's 50% spring and fall freeze dates; higher is better.
• Normal heat + freeze calendar (25%) - calendar days whose normal high is at least 90°F plus days whose normal low is at most 32°F; lower is better. These are normals-based calendar counts, not observed extreme-weather events.
• Summer moisture balance (15%) - June–August mean dew-point distance from 52.5°F; lower is better.

For each dimension, PlainClimate derives live national p10, p25, p50, p75, and p90 breakpoints from all station-mapped records carrying that field, then linearly interpolates the entity's 0–100 percentile score in the stated direction. Equal-valued breakpoints collapse to their mean percentile. Values outside p10–p90 extrapolate toward 0 or 100 using the nearest non-flat segment, then clamp to that range. Dimension scores combine by the weights above. When a field is unavailable, its weight is removed from both the numerator and denominator and the measured weights redistribute to 100%; no value is estimated. At least three dimensions spanning at least two NOAA products are required. Grades are A (85–100), B (70–84), C (55–69), D (40–54), and F (below 40).

The index is one disclosed climate preference model, not an official NOAA rating, forecast, health or safety assessment, or overall quality-of-life verdict. The city scorecard publishes the exact input, source field, weight, per-dimension score, and live benchmark table needed to reproduce the result.

Processing Pipeline

1. Raw NOAA Climate Normals files are downloaded from the NCEI data portal.
2. Station records are linked to cities using NOAA station metadata (station name, state, county).
3. Monthly values are preserved for all 12 months; annual averages are computed where not provided directly.
4. Data is loaded into a structured SQLite database indexed by city, state, and station ID.
5. City pages aggregate available stations; the primary station (typically the airport USW station) drives city-level summaries.

How the Source Agency Collects Data

NOAA Climate Normals are computed from 30 years of weather observations collected through the Cooperative Observer Program (COOP), Automated Surface Observing Systems (ASOS), and other station networks operated by the National Weather Service, the FAA, and volunteer observers. Temperature readings are recorded using calibrated thermometers or electronic sensors following standard siting and maintenance protocols. Precipitation is measured using standard rain gauges, and snowfall is measured using snow boards and snow stakes.

NOAA computes normals using a standardized methodology that accounts for missing data, station moves, and instrument changes. The 1991-2020 normals were computed using the Climatological Linear Relative (CLR) method, which provides more accurate estimates for stations with some missing data compared to simple averaging. Stations must have at least 10 years of data in the 30-year period to be included.

Data Accuracy Commitment

PlainClimate presents NOAA data without modification. Temperature, precipitation, and snowfall values are displayed exactly as computed by NOAA. We do not interpolate data between stations or estimate climate conditions for areas without monitoring coverage. If you find any data that appears incorrect, please contact us and we will verify against the NOAA source data.

Limitations

• Climate normals are 30-year statistical averages, they describe typical conditions, not weather forecasts.
• Not all variables are available at all stations. Smaller cooperative stations may only report temperature and precipitation.
• Station location within a city affects readings. Stations near airports, water bodies, or elevation changes may differ from urban core conditions.
• PlainClimate is an independent information service and is not affiliated with NOAA or the U.S. government.