In short
- Storage Weather measures your startup disk’s free space every 30 minutes and the folders that usually grow once a day, without scanning the whole disk.
- It shows free space over the last 30 days, a forecast after three days of data (“Full in about 40 days”, or “Free space is stable”), and what grew this week.
- It measures while MoreRoom is running. Turn on Open at login, in the menu bar to keep it going with the window closed.
Open it
Click Storage Weather in the sidebar, or the Storage Weather card on the home screen. It works without a scan. The widget and the menu bar item open it too.
What you see
- The forecast — an icon, a title and the space available now:
- Gathering data for the first three days: “MoreRoom measures free space every 30 minutes. The forecast appears after three days.”
- Full in about n days, with how much your Mac loses a day at the current pace;
- Free space is stable when your free space isn’t going down.
- The macOS update card — see Is my Mac ready for the next macOS update?
- Free space, last 30 days — a chart of one point a day. It fills in as days go by.
- What grew this week — the folders that gained the most space in the last seven days, with a button to reveal each one in Finder.
- Two switches: Alert me before my disk fills up and Open at login, in the menu bar.
How it measures
- Free space, every 30 minutes: one quick reading of the disk, the same figure as Finder (purgeable space included). macOS schedules it and defers it when your Mac is asleep, busy or on battery.
- Folders that usually grow, once a day, in the background: developer caches and simulators, Docker and AI models, Downloads, Mail and Messages attachments, iPhone backups, Movies, Steam… plus the largest items of your last scans. Without Full Disk Access, protected folders are left out.
- The history is kept for 120 days, on your Mac only.
It never scans the whole disk, and uses almost no energy.
Keep it measuring
Storage Weather only measures while MoreRoom is running. Closing the window doesn’t quit MoreRoom, but quitting it (⌘Q) stops the measurements. To have it running all the time, turn on Open at login, in the menu bar — in Storage Weather or in Settings › General. See Menu bar and open at login.
Why does the forecast change?
The forecast follows the trend of the recent days. A big download, a macOS update or emptying the Trash changes it quickly; it settles again after a few days. “Free space is stable” means the trend isn’t going down — nothing to worry about.