Instead of the cascading bonuses for current iterative attacks, up to a possible 4th attack at BAB +16, the variant works as follows:
Statistically, you get similar damage output as current iterative attack rules, except at the corner cases when facing foes whose ACs are extremely high or extremely low relative to your attack bonus. The big advantage – fewer rolls, but in particular fewer different bonuses to add! 
The campaign will begin in Early spring.
Day time desert temperatures: Hot DC15 Fort save every hour or 1d4 non-lethal and fatigued
Wearing heavy clothes of any armor adds +4 to the DC.
Sometimes the temperature will increase to Severe Heat: DC15 fort save every 10minutes
There are various ways of protecting yourself, however riding about in the sun in armour looking for things to shoot does not count in anyway towards keeping cool, no matter how fast you are going!
At night the temperature will drop 1 band (severe to hot, hot to warm), though in summer it can drop 2 bands
Above 5,000ft temperature drops 1 band, above 15,000 another band. This means that at night, at high altitude it can be “cold” or “severe cold” which will require cold protection
Although I am not very good at these things… I do plan to expect people to keep track of water and food…