Background <p>Despite advances in cancer treatment, the incurability of the disease is the basis for palliative care.</p> Methods <p>A sample of 334 oncological patients in palliative care underwent a two-year assessment to determine the effects of environmental temperature on mortality.</p> Results <p>The results revealed a positive relationship between environmental temperature and the mortality rates of patients under palliative care, with a higher number of deaths occurring in the warmer months. Thus, a 1ºC increase in temperature correlated with an 8.1% increase in mortality for patients dying in the first week of care, 4.8% for those dying within 15 days, and 3.8% for those dying within 30 days. However, for patients surviving more than 30 days, the effect of temperature decreased, with no significant effects of temperature being observed.</p> Conclusions <p>Thus, environmental temperature could be a relevant factor in the mortality and survival rates of the palliative care program.</p>