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.
1 For more information on flood zones, see FEMA's FloodSmart web page. 2  Zone AE are areas that have a 1% probability of flooding every year (also known as the 100-year floodplain), and where predicted flood water elevations above mean sea level have been established.