Extending operating temperature of storage device

A method of operating non-volatile storage, the method comprising:

• storing a first mapping from one or more logical addresses to one or more physical locations of a first group of non-volatile memory cells in the non-volatile storage;
• folding single level cell (SLC) data stored in the first group at one bit per memory to multi level cell (MLC) data stored in a second group of non-volatile memory cells in the non-volatile storage at multiple bits per memory cell while an operating temperature of the second group of non-volatile memory cells is below a first temperature;
• storing a second mapping from the one or more logical addresses to one or more physical locations of the second group of non-volatile memory cells;
• checking data integrity of the MLC data in the second group after the operating temperature of the second group is above a second temperature that is higher than the first temperature;
• invalidating the second mapping responsive to the MLC data in the second group failing the data integrity check;
• and
• maintaining the second mapping responsive to the MLC data in the second group passing the data integrity check.

A non-volatile storage device comprising:

• a control circuit configured to be connected to non-volatile memory cells, the control circuit configured to:
• access data stored in a first group of the non-volatile memory cells at one bit per memory cell;
• store the data at multiple bits per memory cell in a second group of the non-volatile memory cells while an operating temperature of the second group is outside a first temperature range having a first lower temperature and a first upper temperature;
• check data integrity of the data in the second group after the operating temperature of the second group is within a second temperature range having a second lower temperature that exceeds the first lower temperature and a second upper temperature that is less than the first upper temperature;
• return the data in the second group to a host in response to a request from the host to read data for one or more logical addresses if the data integrity check indicates a bit error rate of the data in the second group is less than a threshold;
• and
• return the data in the first group to the host in response to a request from the host to read data for the one or more logical addresses if the bit error rate of the data in the second group is not less than the threshold.