Ambient Temperature Correction

NEC 2020 — Table 310.15(B)(1)

Ambient temperature (°C)	Ambient temperature (°F)	Temperature rating of conductor
Ambient temperature (°C)	Ambient temperature (°F)	60°C	75°C	90°C
10 or less	50 or less	1.29	1.20	1.15
11–15	51–59	1.22	1.15	1.12
16–20	60–68	1.15	1.11	1.08
21–25	69–77	1.08	1.05	1.04
26–30	78–86	1.00	1.00	1.00
31–35	87–95	0.91	0.94	0.96
36–40	96–104	0.82	0.88	0.91
41–45	105–113	0.71	0.82	0.87
46–50	114–122	0.58	0.75	0.82
51–55	123–131	0.41	0.67	0.76
56–60	132–140	—	0.58	0.71
61–65	141–149	—	0.47	0.65
66–70	150–158	—	0.33	0.58
71–75	159–167	—	—	0.50
76–80	168–176	—	—	0.41
81–85	177–185	—	—	0.29

Multiply the ampacity from the applicable ampacity table by the correction factor for the conductor's temperature rating.

Source: NEC 2020 Table 310.15(B)(1). Verify requirements against the locally adopted code and applicable amendments.