How We Calculate Wedding Weather: Sources, Score And Limits

This page explains how every number on the wedding weather pages is worked out, so you can judge how far to trust it. Each city page links here instead of repeating the explanation.

Where The Weather Numbers Come From

Weather data. The temperature and rain figures are the 1991 to 2020 monthly climate normals published by NOAA's National Centers for Environmental Information. A normal is a 30-year average, so it shows what is typical, not what will happen on your date. Any single year can be warmer, cooler, wetter or drier.

Rain days. NOAA counts the average number of days in a month with at least 0.01 inch of rain (any measurable rain) and at least 0.10 inch (enough to soak an outdoor setup). We use the 0.10 inch figure as the "rained-out" measure for outdoor ceremonies.

How The Outdoor Ceremony Score Works

Outdoor ceremony score. The score is ours, not NOAA's. It starts at 100 and subtracts points for the share of days with 0.10 inch of rain or more, the share of days at or above 90°F, and for average afternoon highs below 62°F or above 84°F. A higher number means friendlier weather for an outdoor ceremony. It is a way to compare months, not a forecast.

As a rough guide, a score of 80 or more means the month is comfortable and dry for most outdoor ceremonies. Between 60 and 80 you can plan outdoors with a backup. Below 40, an outdoor ceremony needs a strong reason, such as an evening start in a hot place.

How Sunset And Golden Hour Are Calculated

Sunset and golden hour. These are calculated from the station's latitude and longitude for the 15th of each month, with daylight saving time applied. Golden hour starts when the sun is 6 degrees above the horizon and runs until sunset. The ceremony start suggestion is 30 minutes before golden hour begins, rounded to the nearest 15 minutes, so portraits fall in the best light. NOAA normals do not include cloud cover, so we do not claim sunny-day odds.

What These Numbers Cannot Tell You

• Your exact venue. Each figure comes from one airport weather station. A venue in the hills, on a beach or across town can run several degrees warmer or cooler.
• Cloud, fog and wind. NOAA's monthly normals don't measure them, so the score can't tell a gray coastal June from a clear one.
• Air quality and smoke. Wildfire smoke is not in the normals. Check the air quality forecast before an outdoor wedding in a smoke-prone season.
• One particular year. A normal is an average of 30 years. Any single year can be warmer, cooler, wetter or drier, and the forecast ten days out is the better guide for your week.

Weather Stations And Coverage

Every place uses the nearest NOAA station that publishes full 1991 to 2020 normals, which is usually an airport. The last column is the smallest number of years of record behind any of the temperature and rain figures for that station.

Browse the results on the wedding weather hub or the California page.