Climate NormsMonthly climate normals by city

Method and sources

Two kinds of content appear on this site: NOAA climate normals we read for each city, and short quotes from a city's local National Weather Service office. Here is how each is handled, plus one open question we have not solved yet.

Climate normals

  1. Which numbers. NOAA's 1991–2020 climate normals: the 30-year average high temperature, low temperature and total precipitation for each calendar month (labelled rainfall on the pages; it counts rain plus melted snow, not rain alone), plus the monthly snowfall normal where the station has one, at one weather station per city.
  2. The exact query. Each city is one ACIS StnData request asking for four monthly elements, all with normal: "1" (the 1991–2020 normal): maxt (average high), mint (average low), pcpn (precipitation, our rainfall column) and snow (snowfall). Where ACIS has no snowfall normal for a station it answers M for every month, and that city page says so instead of showing a snowfall column. Here is the Las Vegas query; every city page links its own.
  3. Which station. Usually the city's main airport station; we name the station and its ACIS station ID on every city page, and link the exact query used to read it.
  4. Where do the numbers come from. We query ACIS — a lookup service NOAA's Regional Climate Centers operate at data.rcc-acis.org — and its stated terms put no restriction on a query of this kind. Our daily allowance there, 30 calls, is split across every site we run, so a city's figures might wait a day or two rather than all landing at once.
  5. Units. Temperatures are shown in °F as returned, with °C alongside (rounded to the nearest whole degree). Rainfall is in inches as returned, with millimeters alongside (rounded). Snowfall is in inches as returned, with centimeters alongside (to one decimal).
  6. What we compute ourselves. The annual average high/low and yearly rainfall total are our own arithmetic on the twelve monthly values (shown in a different style on the page). The hottest/coolest/wettest/driest month is simply whichever month has the highest or lowest of that column.

The "closest to mild and dry" month

Each city page checks its twelve months against one fixed threshold we set ourselves, not any authority's definition of comfort: average high between 65°F and 80°F, and average rainfall under 2 in. Whichever months clear both parts are listed; some cities have several, some have none, and we do not loosen the numbers to force an answer. It is not advice on which month suits any particular trip — it only reports which rows already on the page clear the stated range, so anyone can recompute it from the table.

Local weather office quotes

When a city's National Weather Service forecast office has written a general climate summary, we lift a sentence or two out of it word for word, name the office, and date-stamp the day we read it. Before anything ships, an automated check re-searches our saved copy of that page for the exact quoted wording and blocks the build if it has drifted or vanished. The point of these lines is texture a table can't carry — why a place stays unusually dry, why downtown nights hold their heat — not a second telling of the monthly figures already on the page.

What we have not solved yet: humidity

Average relative humidity is not on this site. The service we read the normals from (ACIS) documents temperature, precipitation and snowfall elements, not humidity, and we only print numbers we have fetched and checked ourselves.

How our fetcher identifies itself

The script that pulls pages and data files sends ClimateNormsBot/0.1 plus a link back to this page — never a browser's user-agent string. Each target's robots.txt is checked first and obeyed, no single host gets hit twice inside a three-second window, and the very first 403, 429 or robots.txt disallow ends the attempt for that host on the spot. We do not swap in a different identity and try again; whatever that source would have given us is simply left out, with only a plain link kept in its place.

Public domain

The National Weather Service's own disclaimer page states its policy on reuse:

The information on National Weather Service (NWS) Web pages are in the public domain, unless specifically noted otherwise, and may be used without charge for any lawful purpose

Source: Disclaimer (National Weather Service); read 2026-09-28.

Pages quoted

Data note

Every city's twelve months were read directly from ACIS by this site's own fetcher on 2026-09-29, one request per city, using the query linked on that city's page. Before that, the site was drafted from a research partner's earlier ACIS reads; our own reads matched those temperature and rainfall figures in every cell.