In addition to risks for humans, electronics in general may have some issues, particularly battery operated equipment. While the equipment might not instantly destruct, extended operation at elevated temperatures will impact long term reliability.
At some point batteries will become a fire risk. Some Li-ion batteries will shut down charging above 45°C. Certainly, keep your battery operated items out of direct sunlight.
Below are some SONOS specific specifications:
Maximum operating temperature:
ROAM: 95°F 35°C
MOVE: 113°F 45°C
Other products: 104°F 40°C
I’ll note that interpreting these specifications is slightly vague in one respect:
Are the portables “operating” if they are simply sitting on their charger or in standby?
While I don’t think that many users would “operate” for extended periods at these maximums, the portables could be thrown in a backpack and carried for a while.