Researchers find that extreme cold reduces risk while heat increases risk of diabetes. According to a published study in the May 15th journal of Canadian Medical Association, it looks like the outdoor temperature can influence a pregnant woman’s risk of developing gestational diabetes. Cold-induced thermogenesis is known to improve insulin sensitivity, which may become increasingly relevant in the face of global warming. The aim of this study was to examine the relation between outdoor air temperature and the risk of gestational diabetes mellitus. Over the 12-year period, there were 555,911 births among 396,828 women. Prevalence of gestational diabetes mellitus was 4.6% among women exposed to extremely cold mean outdoor air temperatures (≤ −10°C) in the 30-day period before screening and increased to 7.7% among those exposed to hot mean 30-day temperatures (≥ 24°C). Each 10°C increase in mean 30-day temperature was associated with a 1.06 (95% confidence interval [CI] 1.04–1.07) times higher odds of gestational diabetes mellitus, after adjusting for maternal age, parity, neighborhood income quintile, world region and year. A similar effect was seen for each 10°C rise in outdoor air temperature difference between 2 consecutive pregnancies for the same woman (adjusted odds ratio 1.06, 95% CI 1.03–1.08). From the findings, it was interpreted that there was a direct relation between outdoor air temperature and the likelihood of gestational diabetes mellitus. Future climate patterns may substantially affect global variations in the prevalence of diabetes, which also has important implications for the prevention and treatment of gestational diabetes. — CMAJ May 15, 2017 vol. 189 no. 19 doi: 10.1503/cmaj.160839