Temperature field can be controlled with the following parameters, which are analogous to Smoke. FumeFX burns unreacted fuel based on Ignition Temperature; and, Temperature Diffusion is the only way to realistically spread the temperature across volume and thus, to help fire propagation.
Master Effector - With Temperature Master Effector you can directly control Temperature channel of each voxel.
Ambient Temperature - Ambient temperature of the grid. If you set this value to a high number (500 for example), most of the air inside the grid would be colder than the ambient air and will cause it to circulate.
Temperature Buoyancy - This value defines how much the fluids will rise in correspondence with the temperature. As fluid is hotter, its density decreases and under the influence of the gravity, it is forced to rise. Positive values will cause hot air to rise and cold air to fall, while negative values will inverse that.
vd Multiplier - This value is used in the case when you are using Variable Density Solver. It is a multiplication factor of Temperature Buoyancy and the final value is used by the vd (Variable Density) solver.
Dissipation Min. Temp - If temperature goes below this value, it will fade according to the Dissipation Strength amount.
Dissipation Strength - The higher this value, the more rapidly temperature will diminish.
Diffusion - This value sets the rate of temperature diffusion. At very high values, temperature inside the grid can drop dramatically. Consequently, if you are simulating burning fuel, the fuel may stop burning; if so, you might need to increase the Heat Production value.
Sharpen - During the simulation the temperature tends to diffuse and dissipate which is generally acceptable for this channel. By using a moderate sharpening value (0.2 for example), the temperature can keep most of the details which might be usable for fire rendering using the Blackbody shader (as it uses the temperature channel for shading).
Sharpen Radius - Defines the width of the sharpening filter.