*3.2. Weather Data*

Because the frequency of use of high-power consumption products such as air conditioners and radiators is closely related to weather [38], weather conditions have generally been used for constructing STLF models in many studies [39]. In South Korea, various weather forecast information including temperature, humidity, wind speed, and so on are provided by the Korea Meteorological Administration (KMA). However, KMA provides weather data using two di fferent time resolutions depending on the type of forecast. Very short-term weather forecast provides weather data up to 4 h by 30 min resolution, and short-term weather forecast provides weather data resolution up to 67 h by 3 h resolution. Since our goal is to predict day-ahead electric energy consumption, we need weather data for up to 24 h. Thus, we used the short-term weather forecast data that have3hresolution and used linear interpolation to calculate 1 h weather forecast data from them. The short-term weather forecast data consists of values such as daily minimum temperature, daily average temperature, daily maximum temperature, temperature, humidity, wind speed, and precipitation, as shown in Figure 2.

**Figure 2.** Example of short-term weather forecast information provided by KMA.

In addition, to establish a more direct correlation between weather data and electric energy consumption, we considered the discomfort index (DI) [40] and wind chill (WC) [41]. *DI* and *WC* are defined using Equations (1) and (2), respectively. Here, *T*, *H*, and *WS* represent the temperature, humidity, and wind speed, respectively.

$$DI = (1.8 \times T + 32) - [(0.55 - 0.0055 \times H) \times (1.8 \times T - 26)]\tag{1}$$

$$\text{WC} = 13.12 + 0.06215 \times T - 11.37 \times \text{WS}^{0.11b} + 0.3965 \times T \times \text{WS}^{0.1b} \tag{2}$$

As a result, we use nine types of weather data (i.e., daily maximum temperature, daily average temperature, daily minimum temperature, temperature, humidity, wind speed, precipitation, discomfort index, and wind chill) for the STLF model construction. Table 5 summarizes an example of weather conditions considered for the input variables.


**Table 5.** An example of weather conditions on December 25, 2018.
