First, let's take a look at the heat scale:
Let's assume that you are starting in a moderate environement - Medium temperature - and want to ramp up the heat as much as possible. You are also level 14, enough to easily get the Greater Drought skill (Walker in the Waste level 9) and therefore have 13 caster levels.
Beginning at 9th level, you can produce extreme desert conditions in a
100-foot radius emanation with you at the center. The temperature band
in that area rises by two steps or to severe heat, whichever produces
the hotter result.
I would recommend using the spell Control Temperature from the Frostburn book.
You imbue an area with cold or fire energy, reducing or raising the temperature by one temperature band per five caster levels.
This lasts for 1 hour/level and has a 20ft/level radius which should be at least 13 hours per casting across a 260ft radius. As a relatively low level spell (third) you should be able to prep multiple castings if needs be.
There are two interpretations of the effects below, depending on whether the spell or the ability are applied to your environment first, but the end result is much the same.
If you add further caster levels, or start in a warmer climate, then you can raise the heat up by another band or two relatively easily.
Greater Drought first
Greater drought raises the temperature in the area to at least severe heat immediately, and at caster level 13 the spell will raise it by a further two heat levels.
At this point you are in Unearthly Heat and everything around you that is breathing will start dying very quickly.
In this temperature band, which includes many environments normally
deadly to all life, unprotected characters take 1d6 points of lethal
damage and 1d4 points of nonlethal damage per round (no save). In
addition, those wearing metal armor or coming into contact with very
hot metal are affected as if by a heat metal spell (which lasts as
long as the character remains in the area of unearthly heat).
Control Temperature first
Starting at Moderate you would add two heat levels from the spell, putting you into the 'Hot' category. Greater Drought then raises this by two steps, taking you into Extreme Heat where everything around you that is breathing will start dying rather quickly, although not as quickly as with the previous example.