I ran into this when running SharePoint migrations using the Microsoft SharePoint Migration tool from File servers to SharePoint Online modern team sites.
The error message “Temporary storage on your local computer is too low. (ErrorCode: 0x02040012)” is a misleading error message and makes you think that you are low on your C drive since the migration logs are saved in “C:\Users\username\AppData\Roaming\Microsoft\MigrationTool\yourdoamin.com”, upon checking the log files, I noticed that were many from the previous migrations and I had a lot of space available on the C drive
The default path for the SPTM tool to dump the log files is as mentioned below. “C:\Users\username\AppData\Roaming\Microsoft\MigrationTool\yourdoamin.com”
One thing that I have tried and that has worked was that you go into the path and delete all the old log files and resume the migrations
below is a Microsoft article related to the above error message
It is possible that it may require certain space available on the C drive to complete the migration and fails if the space starts getting filled up.
Thanks for reading and I hope it has helped with what you were looking for.