Ulcerative colitis (UC) is a subtype of inflammatory bowel disease (IBD) that has been associated with overconsumption of calories and lipids, compared to the healthy population, and summer temperatures have been reported to be closely related to the prevalence of UC. To evaluate the effects of dietary and lifestyle factors on UC, a combination of 2.0% dextran sulfate sodium (DSS), a high-fat/high-sugar diet, and exposure to high temperature and humidity was used to construct mouse models of UC. Changes in body weight, disease activity index (DAI) scores, histopathological analysis, serum lipid levels, serum diamine oxidase (DAO), and D-Lactate (D-LA) levels, as well as the expression of inflammatory cytokines and tight junction proteins in colonic tissue, were all assessed to study the impacts of the high-fat/high-sugar diet and high-temperature/high-humidity exposure on the progression of UC. The symptoms observed in the UC mouse model induced by 2.0% DSS alone were similar to those seen in patients with UC, while the high-fat and high-sugar diet, along with humid and hot exposure, exacerbated DSS-induced UC in the mice. This included more severe histopathological damage to the colon tissue, increased expression of pro-inflammatory cytokines (IL-6, IL-17A, and IL-1β), and a more significantly compromised intestinal barrier, characterized by the destruction of ZO-1 and elevated levels of DAO and D-LA. Additionally, the high-fat/high-sugar diet and high-temperature/high-humidity exposure led to further disturbances in glucose and lipid metabolism in the mice, which were not observed in those treated with DSS alone. This study is the first to investigate the effects of a high-fat/high-sugar diet and high-temperature/high-humidity exposure on the progression of UC.