The maximum operating temperature for copper cable lugs really hinges on their design and how they're treated on the surface. Generally, standard tin-plated copper cable lugs can handle continuous use at temperatures up to 155°C or 149°C (300°F) under typical conditions, as outlined by industry standards and manufacturers. However, if you're looking at specialized copper cable lugs me... https://www.pioneerpowers.com/copper-cable-lugs.php