Abstract: This study focuses on the Changchun area under the influence of the subtropical high and analyzes the relationships between power load and meteorological factors during the high-temperature period in the summer of 2025, including air temperature, relative humidity, wind speed, apparent temperature, and specific humidity. The results show that from July 4 to 12, 2025, Changchun experiences a historically extreme high-temperature event under the influence of the subtropical high. The average temperature is 4.1 °C higher than the climatological normal, ranking first among historical anomalies for the same period. The extreme maximum temperature ranks third for the same period since 1951, and the intensity and duration of the high-temperature event reach the extreme level. Air temperature shows a very strong positive correlation with power load, with R = 0.9. Apparent temperature shows a strong positive correlation, with R = 0.7. Relative humidity shows a moderate negative correlation, with R = −0.5. Wind speed and specific humidity show weak positive correlations, with R = 0.3. These results indicate significant differences in the correlations between different meteorological factors and power load. An air temperature of 31 °C and an apparent temperature of 42 °C can be used as high-load monitoring indicators. When the air temperature exceeds 33 °C and the apparent temperature exceeds 46 °C, these conditions can be used as indicators for initiating emergency dispatch. The proposed indicators provide a reference for power load forecasting under similar weather conditions.