Trapping during summer months can expose small mammals to high temperatures inside traps. We measured trap temperatures under different ambient conditions and levels of sun exposure. Internal temperatures of Sherman traps exposed to full sun were 14% higher than those exposed to full sun and fitted with a corrugated cardboard cover and tent. Traps with the surrounding cardboard cover and tent experienced up to a 7.6 °C reduction in internal temperature and could be left out one to two hours longer on average than traps exposed to full sun before internal trap temperatures rose into the minimum lethal range for most small mammal species.