Fahrenheit also has to engage in a little trickery, should the temperature ever drop below zero. Negative numbers can't appear in alert badges, so you have the option to display that temperature as a positive number; you can have Fahrenheit send you an alert when the temperature falls below zero. As I live in California, I will have far graver concerns than whether my iOS app is showing a positive or negative temperature should the mercury dip that low, but it's a feature that users in colder parts of the country should be aware of.

As with the built-in Weather app, you can add multiple cities in Fahrenheit. (I'm not sure how many exactly--I added 15 cities before I got bored. Add too many, though, and the navigational cues at the bottom of the screen become a little tough to negotiate.) That's a nice feature, but it also brings up Fahrenheit's biggest shortcoming--one that's really out of the developer's control. The home-screen temperature will only be tied to one location you designate in the settings screen; because of limitations in the current version of iOS, that temperature won't change to reflect your location. In other words, if you tie Fahrenheit in to your home in a warm inland valley, the home-screen temperature won't reflect the conditions after you've commuted to your job in a cool-weather city on the coast. It's not a deal-breaker by any means and, as I said, it's out of the developer's hands anyway. But it does mean that Fahrenheit is a marginal improvement over the built-in Weather app when, with a more accommodating operating system, it could be a substantial improvement. Still, for $1, the convenience of a home-screen temperature and the depth of information contained within the app itself makes Fahrenheit a solid addition to your iPhone or iPod touch. And on the iPad, which doesn't come with a default Weather app, Fahrenheit is a great low-cost, high-value option.