Does anyone know of a web site or iPhone app that will give a rough tide prediction several months into the future? I'm not worried about fine details, just when it will be high or low within an hour or two.

I can't find any web site that goes more than a week or two out. Descriptions I've read in the app store have not been useful. That's not very useful when trying to plan a trip along the California coast in April.

Yes, I could watch the tides for a few days, figure out the average time between high tides, and work it out for myself, but I'm hoping I don't have to.