Get your head out of the Cloud. Apple announced Sept. 24 that some iCloud users will soon lose 20GB of free storage space.

Users who migrated from MobileMe to iCloud are vulnerable to losing the 20GB of storage. Apple has notified iCloud customers via email that the complimentary 20GB will expire Sunday, Sept. 30.

The move only affects users who had previously paid for MobileMe, the synchronization and storage predecessor to iCloud. While iCloud is free to all Mac and iOS device owners, MobileMe cost $99 annually for, among other things, 20GB of online storage space.

Apple has steadily increased the storage levels for its users through years of its cloud-based offerings,  allowing them more options for distributing storage for various account services including iDisk and e-mail. The storage level for a basic account peaked at 20GB for a free MobileMe account, and could be split among its e-mail and iDisk services depending on what the user needed.

iCloud offers 5 gigabytes of free storage for mail, documents, and backup. Purchased music, apps, and books don't count against the 5GB.

During the switch from MobileMe to iCloud -- a process that started in 2011 and ended June 30, 2012 -- Apple offered an additional 20GB of storage to MobileMe subscribers as a way to temporarily tide them over. The 20GB was atop the standard 5GB all iCloud users received as part of the free package. The end of the free storage ride had originally been set for June 30, 2012 -- the date MobileMe went dark -- but in May Apple extended the deal by three months.

Now Apple is taking away the 20GB, telling customers that to keep it they must fork over $40 a year.

From Apple:

"Dear ICLOUD USER,

Your iCloud storage will be reduced to 5 GB on 09/30/2012. However, you are currently using more than 5 GB.

Unless you take action before your downgrade takes effect, backups to iCloud will stop, and apps will no longer be able to save documents to iCloud. You can either free up storage or cancel your downgrade to keep your current storage plan for another year.

To free up storage in your account:

Step 1:

On your iOS device, go to Settings and tap iCloud

Step 2:

Tap Storage & Backup

Step 3:

Tap Manage Storage and choose items you'd like to delete or stop backing up For more information on managing your iCloud storage, please read this article.

To keep your current storage plan:

Step 1:

On your iOS device, go to Settings and tap iCloud

Step 2:

Tap Account

Step 3:

Tap your current plan, then choose Downgrade Options and follow the prompts You can also cancel your downgrade from a Mac or PC."

If you're an iCloud user that hasn't used your 5GB of storage space during the transitional period, then your storage levels will switch automatically without you having to do anything. But, if you've been using more than the 5GB, then you'd better start clearing out your documents or purchase more storage from Apple now.

If you are currently using more than 5GB of storage, Apple will not delete your data if you do not upgrade, but new storage to your iCloud account will be frozen until you remove items to bring your storage levels below the new 5GB limit. This means that not only will you be unable to upload and sync files, but you will also not be able to receive any new e-mail. During this time, iCloud will inform you that you have exceeded your limit and offer links to support documents on how to upgrade or remove items from your iCloud storage.

To free up iCloud storage in OS X, go to your iCloud system preferences pane and click on the Manage button at the bottom of the window. In the new panel that appears you can select a program or service category to see what documents are being stored in iCloud by that service. The overall amount of storage used by that service will be listed underneath it.

While you can manually delete documents and backups from iCloud using the OS X system preferences, e-mail must be managed through Apple's Mail program or another e-mail client you are using to access your iCloud mail.

Users who want to retain the 20GB of iCloud storage must pay $40 per year to upgrade (to 25GB total; the free 5GB plus the 20GB). Apple also offers 10GB additional for $20 and 50GB for $100.

Apple's 20GB and 50GB prices are four times what Microsoft charges for extra Skydrive storage. Skydrive allots 7GB of free storage, and then charges $10 per year for 20GB more and $25 for an additional 50GB. Microsoft also has a 100GB plan priced at $50.