My binary planets are roughly the size of earth and they are tidally locked with one another. Both planets support life. If the day/night cycle is roughly 100 hours (50 hours of day, 50 hours of night), how widely would the temperature vary from the warmest part of day to the coldest part of night?
The distance between the planets is approximately 12,000 miles (19,312 km). I came up with this distance from this article, http://phys.org/news/2014-12-binary-terrestrial-planets.html, which suggests the centers of the two planets would be separated by approximately three planet radii.
The distance from the planets to their star is at least 1/2 an astronomical unit but they could be much further away. The planets are orbiting each other in the same plane as they orbit their star so they experience a solar eclipse once a day. Axial tilt is zero. The atmosphere on both planets is similar to Earth's atmosphere. I would like to keep the average temperature as similar to Earth as possible.
I believe temperatures would vary less near the coasts and more inland, and humidity would also decrease variance in temperature.
With such long days and nights, is a diurnal temperature variance of 50-75F possible in certain areas? I need these planets to support life.