AT&T has officially announced the pricing and availability of the Nokia Lumia 635. The Windows Phone 8.1 smartphone is set for $99 off-contract in August.

T-Mobile kicked off bringing the first Windows Phone 8.1 smartphone to U.S. customers in the beginning of July when the carrier began offering the Nokia Lumia 635. The handset has been marketed as a replacement for the very popular Lumia 520, which Microsoft recently announced had sold over 12 million units, making it the most popular Windows Phone ever.

The Nokia Lumia 635 will be making its way to AT&T very soon and it offers smartphone users a larger 4.5-inch ClearBlack display compared to the 4-inch screen found on the Lumia 520 series and its other main features are Windows Phone 8.1 out of the box and its very attractive $99 off-contract pricing.

Windows Phone 8.1 includes "Action Center," which shows you any new notifications and access to commonly used settings. It is accessed the same way Android and iOS users have gotten used to, a simple swipe down on the smartphone's display. Another iOS and Android feature Windows Phone 8.1 brings to the table is called Cortana. This is Microsoft's answer to Siri and Google Now. Cortana uses a virtual notebook to securely store what the assistant learns about its user over time and can make more precise suggestions.

The AT&T Nokia Lumia 635 features a 4.5-inch 854 x 480 ClearBlack IPS (in-plane switching) display and runs Windows Phone 8.1. It's powered by a 1.2GHz quad-core Qualcomm Snapdragon 400 processor and 512MB of RAM. Nokia has included 8GB of internal storage and a microSD expansion slot that will support up to 128GB microSD cards.

The Lumia 635 ships with a single 5-megapixel rear camera with 4x digital zoom and autofocus. It also includes a 1,830 mAh removable battery that will provide up to 11 hours of talk time and 19 days of standby time.

AT&T has announced that it will begin offering the Nokia Lumia 635 on August 8 for a "special launch price of $99.99" on July 25. It will offer the smartphone online and in retail stores on August 8 and will include a black and orange cover in the box for $139.99 off-contract. Check out the video below to get better acquainted with the Nokia Lumia 635.