Evaluating cooling effects within local climate zones (LCZs) is vital for urban planning, especially in countering urban heat islands and enhancing thermal comfort. While prior research has primarily focused on the influence of land cover type LCZs on land surface temperature in large cities, the role of LCZ characteristics across diverse urban environments in smaller regions remains insufficiently explored. This study investigates the cooling effects of land cover type LCZs within the urban built-up areas at the county level using ECOSTRESS land surface temperature data. We utilized a random forest regression model to assess the impact of LCZ factors—namely, landscape shape index, percentage of landscape, and nearest neighbor distance among six built type LCZs and three land cover type LCZs—on cooling effects. The key findings are as follows: (1) Densely constructed LCZs demonstrated higher land surface temperature due to increased heat retention, with LCZ2 showing the highest mean land surface temperature (37.64 °C), whereas land cover type LCZs, particularly LCZG, recorded significantly lower mean land surface temperature (31.86 °C). (2) Land cover type LCZs were crucial in reducing land surface temperature, with LCZG presenting the most significant cooling effects, ranging from 0.31 to 79.43. LCZA and LCZD displayed comparable cooling effects, with average values of 6.54 and 6.46, respectively. (3) The landscape shape index of the land cover type LCZs themselves contributed most significantly to cooling effects. The percentage of landscape and landscape shape index of LCZ3 and LCZ6 notably influenced cooling effects in LCZA and LCZD, while LCZ5 predominantly affected LCZG. (4) The interactions between key factors and cooling effects were found to be complex and nonlinear. U-shaped effects were observed (e.g., central percentage of landscape affecting LCZA and LCZD, and percentage of landscape in LCZ6 affecting LCZG), alongside inverted U-shaped effects (e.g., landscape shape index in LCZ6 affecting LCZG) and combined effects (e.g., landscape shape index of LCZ3 affecting LCZA). The results emphasize the significance of maintaining contiguous and well-structured land cover type LCZs to optimize cooling effects.