What temperature range defines the USDA Temperature Danger Zone relevant to sun tea safety?
$40^ ext{o} ext{F}$ and $140^ ext{o} ext{F}$ ($4^ ext{o} ext{C}$ and $60^ ext{o} ext{C}$)
The United States Department of Agriculture (USDA) explicitly defines the temperature danger zone for food safety as the range between $40^ ext{o} ext{F}$ ($4^ ext{o} ext{C}$) and $140^ ext{o} ext{F}$ ($60^ ext{o} ext{C}$). This range is critical because if bacteria—which may be present in the water, tea, or container—are present, this lukewarm environment allows them to multiply rapidly. The danger with sun tea is that the water temperature can easily hover within this zone for hours as it warms up initially, or if the ambient sun intensity is low and prevents the water from surpassing the $140^ ext{o} ext{F}$ threshold. Since the water is not being brought to a boil, any existing pathogens are not killed, making this prolonged exposure the central food safety hazard cited by experts.
