What temperature does it have to fall below in the office before a employer is legally obligated to send you home?

There is no specific temperature set by federal law in the United States that requires employers to send employees home due to cold conditions in the office. However, many states and local jurisdictions have their own regulations regarding workplace safety and health, which may include guidelines for minimum indoor temperatures. Generally, if the temperature falls below a level that poses a risk to employee health or safety, employers are encouraged to take appropriate action, such as providing heating or allowing employees to leave. It's essential to check local labor laws for specific requirements.