Offline means the weather you downloaded is on the phone and everything that uses it keeps working: the chart's layers, the time bar, the forecast at a place, and routing on the phone. What stops is anything new: no newer run, no fresh warnings, no server routing.
What keeps working
- The chart's weather and the time bar, for as far as the forecast reaches.
- The forecast at a place, anywhere inside the area you downloaded.
- Route from here, on the phone, with a routing pack and its land and depth data.
- Importing a GRIB file that arrived another way.
- Charts you downloaded. See Get charts for your area.
How old is the forecast
A forecast does not get better with age. Three places tell you:
- The time bar. The run line under the time turns amber, then red with a warning triangle, as the run ages.
- Held forecasts. On the Get tab, under Held, tap Held forecasts. Each is listed with its age and a badge: Latest, Newer run out, or Stale. A download that stopped short says how far it reaches. Tap one for its model, run, valid times, area and parts.
- Readiness. The project and the Go sailing sheet flag a missing or stale forecast before you leave.
Storage
Forecasts take space. Open Settings › Weather storage.
- Held shows how much the forecasts take, against a bar to the Limit. The limit starts at 500 MB; step it up or down.
- Over the limit, expired forecasts are removed first, then runs a newer one replaces, then the least recently used. Would be removed lists them before anything goes; hold Remove now to remove them at once.
- Pin a forecast, by swiping it right, to keep it whatever happens. Pinned forecasts are never removed.
- Delete a forecast by swiping it left and confirming.
Weather is not included in the phone's backups.
Limits
Download before you lose the link. The phone cannot fetch a newer run offshore without a connection, though a satellite link or satellite mail can bring one in.