Bill Gillam, a tech enthusiast from Arlington, Washington conducted a test of an Apple iPad on a sunny with 63°F outdoor temperature.
Armed with an expensive FLIR camera — a device that captures images in the infrared spectrum and reports temperatures of surfaces in the image — Bill Gillam checked the temperature of an Apple iPad used in direct sunlight. He took note of the elapsed time when the device shut down. After 11-12 minutes of use in direct sunlight, the iPad screen went dark with a temperature alert displayed on the screen. The device read a temperature of 97°F at the center of the iPad screen with an average temperature on the device of about 100°F. The shutdown is temporary.
Evidence points to the idea that the device is great in the house, in the kitchen, on the coffee table, etc., but it might not be the workhouse for heavy duty mobile workers.