About tidesnearby

tidesnearby is a tide planning guide for 12 California beaches, from San Francisco in the north to San Diego in the south. It is built to answer the questions people have before they drive to the coast: when the next low tide is, which day this month is good for tide pooling, and when the highest tides and grunion runs are expected.

Who runs the site

tidesnearby is an independent site, built and maintained by one developer. It is not affiliated with NOAA, the California Department of Fish and Wildlife (CDFW), California State Parks or any other agency.

The tide numbers come from NOAA's published predictions and are refreshed every week. Local facts, such as where the tide pools are and which rules apply, are checked by hand against official sources before they go on a page. To report a wrong time or a fact that has changed, email the address on the contact page; corrections go into the next update.

What the site does

Tide sites usually list stations. Ours is organized around the places people go. Each of the 12 place pages is named after a beach town or city, and it gives one NOAA station's predictions for that place, with the station's name and how far away it is printed next to the numbers.

A place page leads with the next low tide and a chart of the water level, followed by a week of high and low tides and the days worth planning for. For tide pooling we flag tide pool windows: low tides between sunrise and sunset at 1.0 ft or lower. 11 of the 12 pages have a tide pool section (San Francisco, Half Moon Bay, Santa Cruz, Monterey, Pismo Beach, Santa Barbara, Malibu, Newport Beach, Laguna Beach, La Jolla and San Diego); Huntington Beach does not, so its page shows no tide pool ratings.

The site also has a few pages that compare places or cover one topic:

The California tide charts page compares the next low tide, the best tide pool day and the highest predicted high tides across all 12 places.
The California grunion run schedule lists the runs that the California Department of Fish and Wildlife expects.
The solunar calendar gives major and minor periods, worked out from the moon for each place.
The guides explain how to read a tide chart andwhich tide is best for fishing.

The place pages, from north to south:

How the pages are made

Tide numbers come from NOAA, not from a person

Every tide time and height on the site comes from the tide predictions published by NOAA's Center for Operational Oceanographic Products and Services (CO-OPS). A script downloads them for 14 NOAA stations, and the pages are rebuilt from that download once a week. No tide time is typed in by hand. The predictions on the site now were downloaded on Thursday, October 1 at 11:40 PM, Pacific time.

Each place has one main station, and no two places share a station. San Francisco and San Diego also use a second station, for one named section only. Thedata sources page lists every station with a link to its NOAA page, and explains how we draw tide curves for stations where NOAA publishes only the high and low tides.

Sentences that change with the data

Much of the text on a place page is written from the predictions as well: which day has the lowest tide, the week's biggest swing between high and low water, how many tide pool windows the next 30 days hold. Those sentences change when the tides do, so they are rebuilt with the numbers each week. Charts are drawn when the site is built and work without JavaScript; a small script in the page keeps the "right now" parts current between rebuilds (the water level, the countdown to the next tide, today's tide pool window), using only the predictions already in the page.

Local details are checked by hand

Local details, such as where the tide pools are or which rules apply on a stretch of shore, are written for each place and checked by hand before they go on the site. Rules about collecting, fishing or grunion link to the agency that sets them, such as the California Department of Fish and Wildlife or the park that manages the shore. If we are not sure a detail is still true, we leave it out rather than guess.

What the site is not

The tide numbers are predictions, not readings from a gauge. Weather, such as wind and air pressure, can make the real water level higher or lower than predicted. The site is for planning a visit to the beach; it is not for navigation.