Interestingly, unpowered flash memory has much higher retention rates at low temperatures and much SHORTER retention rates at elevated temperatures (the typical JEDEC spec is just 1 year retention at 30C unpowered).
None of that is particularly surprising, but what's interesting is that write endurance can have the opposite effect... Writing at high temperature (followed by cooling to ambient... or lower) actually improves data retention over just writing at ambient.
Flash memory in a freezer (assuming you don't have cold-induced circuit board failures due to CTE mismatch) could last hundreds of years. In a hot car, maybe a month. https://www.curtisswrightds.com/media-center/blog/extended-t...
None of that is particularly surprising, but what's interesting is that write endurance can have the opposite effect... Writing at high temperature (followed by cooling to ambient... or lower) actually improves data retention over just writing at ambient.