Second Sun for income

[shatner]

I've never used this spell, nor have I ever seen it used (I doubt I'm alone in that). As such, I don't know to what extent that global works. Does it only shift the temperature three steps (so neutral to heat-3 or cold-3 to neutral), or does it just continue to shift the temperature until even a cold-3 nation is suffering from heat-3? Does it stack with the temperature shifts caused by the seasons? If it causes a max of three temperature shifts than Shangrila00's idea is pretty sound. If not, it really only makes sense for nations that have high heat preferences by default.