Threat of paediatric hyperthermia in an enclosed vehicle: a year-round study.

Objective: To describe temperature change throughout the workday in an enclosed vehicle in Austin, Texas across the calendar year while accounting for heat index.

Methods: In this observational study, vehicular temperature was measured 1 day per month during 2012 in Austin, Texas. Data were recorded at 5-min intervals via an EL-USB-1-PRO digital temperature sensor from 8:00 to 16:00. Selected days were primarily cloud-free (with 'clear' or 'few clouds') with a predicted ambient temperature high within ±20°F of the 30-year normal high. Referent temperature and 30-year normal data were collected via the nearest National Weather Service (NWS) weather station. The NWS heat index and corresponding hazard levels were used as a guideline for this study.

Results: Per NWS guidelines, the enclosed vehicle temperature rose to 'danger' levels of ≥105°F (41°C) in all months except January and December and to 'extreme caution' levels of ≥90°F (32°C) in every month of the year. In June, the vehicle rose to ≥105°F (41°C) by 9:25. The hottest vehicular temperature achieved was 137°F (58°C). In 9 months of the year, the vehicle reached ≥90°F (32°C) by noon. We also found that an ambient temperature as low as 68°F was associated with vehicular temperatures ≥105°F (41°C).

Conclusions: Infants and children in states that experience mild winter temperatures face the threat of vehicular hyperthermia disability and death across the calendar year. Prevention efforts that focus on awareness of a childhood heat vulnerability, parental perception of susceptibility to forgetting a child in a vehicle and universal availability of vehicular safety devices may reduce paediatric vehicular hyperthermia death.