Acetylcholine. in CNS and PNS: generally excitatory but is inhibitory to some organs and glands; an organic, polyatomic ion that acts as a neurotransmitter in both the peripheral nervous system (PNS) and central nervous system (CNS) in many organisms including humans.
So Zone 3 is more typical of North Dakota, while Zone 9 is lovely Florida weather. Each hardiness zone differs by 10 degrees F, so the difference in low winter temperatures between zones 6 and 7 is 10 degrees; between zones 6 and 8, 20 degrees; between zones 6 and 9, 30 degrees, and so on.
About 14 percent of the population lives in areas above 2,400 meters (cool climatic zone), about 75 percent between 1,500 and 2,400 meters (temperate zone), and only 11 percent below 1,500 meters (hot climatic zone), although the hot zone encompasses more than half of Ethiopia's territory.