Weather and Tides - from the Official Tourism Website for the Isles of Scilly

Weather

If you ask a boatman for a weather forecast you're most likely to hear that 'it's sunny on all the off-islands.' However if you're looking for something slightly more accurate look no further. We've put together a shortlist of the best Isles of Scilly weather forecasting services.
BBC - general forecast
WINDFINDER - marine forecast
METCHECK - today and tomorrow in depth

Tidetables

Do you want to picnic on 'The Bar' or watch seals basking in the sunshine at low water in the Eastern Isles? Perhaps you're hoping to plan your holiday around spring tides when it is possible to walk between some of the islands. Whatever you're looking for a tide timetable can help with your holiday planning. Click here for St. Mary's tide times for the next 28 days. Or alternatively the Tourist Information Centre sell tide tables by mail order. Ring 01720 424031 for more details.
PROUDMAN OCEANOGRAPHIC tidal predictions