Research conducted in 2014–2023 identified meteorological and bioclimatic features at Lake Piaseczno (Łęczna–Włodawa Lake District) during the warm halfyear (April–September). The presence of the lake contributed to higher relative humidity (1–7% above the station in eastern Lublin) and more frequent night cooling below 15℃, reducing warm and tropical nights. Hot days occurred more often at the lake, while very hot days were more frequent in the city due to higher maximum temperatures. The diurnal cycle indicated stronger nocturnal cooling near the lake and greater daytime heating in the city. Analysis of the Humidex index showed that comfort conditions occurred more frequently at night and in the morning at the lake, while during the day higher humidity contributed to stronger discomfort. The findings confirm the complex local climatic effect of the lake: mitigating at night and in the morning, yet enhancing thermal discomfort during the day.