The phrase "average temperature" refers to the overall or typical temperature over a certain period of time, taking into account highs and lows. It represents the general or normal temperature experienced during that time. Full definition
The error of each estimate of global average temperature of an ocean layer remains closer to that of the instruments, or about 0.1 C. (joannenova.com.au)
Global warming is the increase in average temperature of the oceans and air near the earth's surface occurred. (slideplayer.com)
Global warming The steady rise in global average temperature in recent decades, which experts believe is largely caused by man - made greenhouse gas emissions. (bbc.com)