According to ICAO ISA conditions at sea level, what is the standard temperature?

The standard temperature at sea level according to International Civil Aviation Organization (ICAO) International Standard Atmosphere (ISA) conditions is +15°C. This temperature is established as a baseline for assessing altitude and performance in aviation. The ISA model is used worldwide for various calculations and standardization in aeronautics, providing a consistent framework for pilots and engineers to assess aircraft behavior and performance under a standard atmospheric condition.

By maintaining a defined sea level temperature of +15°C, aviation professionals can accurately predict how aircraft will perform at various altitudes and under different conditions. This standardization is key in flight planning, as it helps ensure safety and efficiency during operations.