No, it doesn't do grep. Long-time developer Bare Bones Software has branched out from feature-rich applications like BBEdit and Mailsmith with the $10, a System Preferences pane that has a single purpose in life: to populate iCal with weather forecasts so you can better plan for upcoming local events and trips to far-off spots.
WeatherCal's interface is minimal, letting users create calendars for multiple locations by clicking the plus (+) button. You can find locations by name, ZIP code, and airport code, but WeatherCal automatically creates a default location by reading the location from the entry you've designated as "My Card" in Address Book. You can edit each location's name as desired, and deselecting a location's checkbox removes its events from your calendar without deleting the calendar itself. Removing a calendar entirely is merely a matter of selecting it and clicking the minus (-) button.
Once configured, WeatherCal creates a normal iCal calendar for each location, displaying the current conditions for the current day and a simplified forecast for the next five days. (Bare Bones tells me that sometimes the weather feeds provide more than five days of forecasts for U.S. locations, and sometimes less than that for international locations.) As with all other iCal calendars, you can set the color of the calendar by selecting it in iCal, pressing Command-I, and choosing a new color from the pop-up menu.
Double-click one of WeatherCal's events and you'll see a URL that will load the Weather Underground Web page for that location, making additional information a mere three clicks and an application change away.
The calendars are rolling, meaning that you'll only ever see events for the current day and the next five days; WeatherCal tidies up after itself so you don't have past weather conditions cluttering your calendar.
Being normal iCal calendars, they'll also sync to your iPhone or iPod, and will display with any iCal-savvy utilities like Second Gear's, which provides an at-a-glance view of your events and tasks in iCal.
And well, that's it. WeatherCal is a one-trick pony, but it's a clever trick, and a useful one to boot. With it, you can easily tell, when making plans for next weekend, if the weather is likely to be amenable for a picnic. And if the drivers in your area freak out with a little rain or snow, knowing the forecast when making plans for a meeting across town next week could save you from an unpleasant traffic jam. Or, if you're planning a trip to Macworld Expo next year, adding San Francisco to your calendar ahead of time will give you a sense of how to pack.
Obviously, there are a ton of ways to find weather information on the Internet these days, but context is king, and having weather information in your face while you're making plans is, in my mind, worth 10 bucks. WeatherCal requires Mac OS X 10.5 or later, and is a 2.6 MB download.
I'm a minor weather geek, to the point where I regularly check out the on the Web and buy the Ithaca Weather Calendar each year for its updated almanac information. From that standpoint, I can see a few features Bare Bones could implement for WeatherCal 2.0. iCal events have a Notes field that would be perfect for textual forecast information, for instance. (Bare Bones said that parsing that information in a reliable fashion is non-trivial.) Plus, since WeatherCal knows current conditions, it could optionally create another calendar in iCal with the high and low temperature for each day, enabling users to go back to see what the weather was like in the past. Nevertheless, these are trivial suggestions - WeatherCal seems fully baked as it stands, and I look forward to using it throughout the upcoming seasons.