Looking at Venus, Earth and Mars, the closer you are to the Sun the warmer you are. At the same time the warmer planets also have thicker atmospheres.
|Venus||870 °F (465 °C)||870 °F (465 °C)|
|Earth||-129 °F (- 89 °C)||136 °F (58 °C)|
|Mars||-195 °F (- 125 °C)||70 °F (20 °C)|
Source for temperatures in the table: earthguide.ucsd.edu.
Mars does not have an significant magnetic field which is problematic on several levels for terraforming. There are several issue with keeping an atmosphere on Mars and some potential solutions. For this question please assume the issues with maintaining an atmosphere are addressed.
Given sufficient atmosphere, would Mars have temperature ranges similar to Earth? If so, would the atmosphere required to keep it warm, be problematic for any human to breathe?