Methodology & data sources
Transparency is the core of our E-E-A-T: this page documents where our data comes from, how often it changes, and the formulas behind every derived figure on the site.
Data source
All temperature, precipitation and snowfall figures are NOAA NCEI U.S. Climate Normals for the 1991–2020 period — the official 30-year reference dataset published by the U.S. National Oceanic and Atmospheric Administration. The values are a U.S. Government work in the public domain (CC0). For each of our 40 cities we record the specific weather station used (shown on the city page) and verify the monthly normals against the published source.
| Source | Refresh cadence | License |
|---|---|---|
| NOAA NCEI U.S. Climate Normals (1991–2020) | none | U.S. public domain / CC0 |
| NOAA National Weather Service (NOWData / local climate pages) | none | U.S. public domain / CC0 |
Climate normals are recomputed by NOAA roughly once a decade (the next update will be the 2001–2030 period), so this snapshot does not need frequent refreshing — hence the "none" cadence.
What "climate normal" means
A climate normal is the 30-year average of a weather measurement — for example, the average daily high in July across 1991–2020. It describes what is typical for a place and month. It is not a forecast: any individual day or year can be much warmer, cooler, wetter or drier than the normal. Read our guide on what climate normals are for more.
How "best time to visit" is computed
The "best time to visit" on each city page is derived transparently from that city's own normals. We select the months whose average daytime high is in the comfortable 60–82°F range and whose average precipitation is at or below the city's monthly average. Contiguous qualifying months are reported as a range. If no month qualifies — for instance a city that is always very hot or always cold — we fall back to the three months whose average high is closest to an ideal 72°F. The rule weighs comfort and dryness equally and ignores humidity, wind and daylight, which are matters of personal preference.
How the rankings and tool work
Rankings sort cities by a single normal (e.g. average January high, total annual precipitation) or a simple documented composite (the winter-getaway score is the average Dec–Feb high minus a rainfall penalty). The packing & comfort index applies fixed temperature and precipitation thresholds to a city's monthly normal. All computation runs in your browser from the same committed dataset; we store no inputs.
Limitations
Figures are 30-year averages and may not match the weather on your specific dates. Station location (airport vs city centre) can shift values by a few degrees. We do not model humidity, wind chill, heat index or microclimates. Always check a live forecast before you travel. See our disclaimer.