United States · coast guide
Understanding the coast of United States
This guide explains the coast of United States on the Atlantic, the Pacific, the Caribbean; calculations, observations and product limits remain distinct.
Read a local tide
Times and heights depend on the port, datum and station timezone. The United States spans Atlantic, Gulf, Pacific, Caribbean and Great Lakes settings. NOAA distinguishes station tide predictions from observed water levels, and Great Lakes levels follow a different regime from ocean tides. Keep the named station, datum and product type with the value you use. A value from another place cannot be carried to a nearby beach. Mareloa preserves the source and timestamp of its data but does not replace the national hydrographic reference.
Tidal range and coast
Ranges vary between estuaries, open Pacific coasts, Gulf shores and island waters. A high or low tide from one coast is not a national measure of beach access. Start with the local station and use published local information for the particular shore, harbour or trail. Tidal range is the vertical difference between low and high water. Bays, depth and coastal shape change it, so one astronomical cycle does not create the same range everywhere. Mareloa creates no national coefficient for United States and infers no access from one number.
Prediction, model and observation
A harmonic prediction is periodic; a measured level is a station observation. Wind, pressure, waves and weather can affect conditions, especially where the source presents marine warnings separately. Do not turn one product into another or treat missing observations as a benign condition. An astronomical prediction calculates a periodic component. A model adds assumptions; an observation is a measurement at a station and time. Wind, pressure, waves and geography can change actual level. These categories remain separate and missing evidence never becomes reassuring.
Plan a coast visit
Beach closures, shellfish advisories, protected areas and access rules come from state, tribal, federal or local authorities. Check the authority that manages the actual place and current on-site notices before a visit. The guide is explanatory and does not make a safety or permission decision. Use this guide to understand provenance, not to decide an activity. Restrictions, health notices, access and signage are local and can change. Consult the competent authority and on-site information; Mareloa is not a navigation tool.
Reviewed source
This page cites and links to this public reference; it does not reproduce its tables.
Reviewed 2026-09-11.