For those who do not know what your plant hardiness climate is:
Wikipedia
https://en.wikipedia.org/wiki/Hardiness_zone#USDA_hardiness_zones Zone From – To From – To
0 – a < (−65° F) −53.9° C
0 – b (−65° F) – (−60° F) −53.9° C – −51.1° C
1 – a (−60° F) – (−55° F) −51.1° C – −48.3° C
1 – b (−55° F) – (−50° F) −48.3° C – −45.6° C
2 – a (−50° F) – (−45° F) −45.6° C – −42.8° C
2 – b (−45° F) – (−40° F) −42.8° C – −40° C
3 – a (−40° F) – (−35° F) −40° C – −37.2° C
3 – b (−35° F) – (−30° F) −37.2° C – −34.4° C
4 – a (−30° F) – (−25° F) −34.4° C – −31.7° C
4 – b (−25° F) – (−20° F) −31.7° C – −28.9° C
5 – a (−20° F) – (−15° F) −28.9° C – −26.1° C
5 – b (−15° F) – (−10° F) −26.1° C – −23.3° C
6 – a (−10° F) – (−5° F) −23.3° C – −20.6° C
6 – b (−5° F) – (0° F) −20.6° C – −17.8° C
7 – a (0° F) – (5° F) −17.8° C – −15° C
7 – b (5° F) – (10° F) −15° C – −12.2° C
8 – a (10° F) – (15° F) −12.2° C – −9.4° C
8 – b (15° F) – (20° F) −9.4° C – −6.7° C
9 – a (20° F) – (25° F) −6.7° C – −3.9° C
9 – b (25° F) – (30° F) −3.9° C – −1.1° C
10 – a (30° F) – (35° F) −1.1° C – +1.7° C
10 – b (35° F) – (40° F) +1.7° C – +4.4° C
11 – a (40° F) – (45° F) +4.4° C – +7.2° C
11 – b (45° F) – (50° F) +7.2° C – +10° C
12 – a (50° F) – (55° F) +10° C – +12.8° C
12 – b (55° F) > +12.8° C
USDA Interactive Plant Hardiness Map URL - enter your zip and it'll tell you down to the a or b
http://planthardiness.ars.usda.gov/PHZMWeb/Default.aspx Where you can purchase a 40x 60 USDA Plant Hardiness Map
http://whmap.com/plant-hardiness-zone-map/I do like the global warming dance around the USDA did. They stated that the 10 degree higher difference was NOT a statement on global change but the result of different data gathering methods.
One final note - there micro-climates in various places. Those generally fall into a different number from the surrounding area.