Table 3.

Excess relative risk and excess absolute risk (95% confidence interval) of emergency department visits for any cause associated with extreme heat over lag days 0-5, by US Global Change Research Program’s Fourth National Climate Assessment (NCA4) region and Köppen-Geiger climate zone

Characteristics	No of counties	Median temperature (°C)	Extreme heat* (°C)	Excess relative risk† (%)	P value	Excess absolute risk† (No/100 000 persons at risk/day)	P value
Climate zone
Continental	1268	26.6	32.9	10.6 (9.8 to 11.3)	<0.001	10.5 (9.9 to 11.2)	<0.001
Temperate	1388	30.9	35.4	6.0 (5.3 to 6.6)		6.8 (6.1 to 7.4)
Dry	278	30.3	36.7	5.8 (4.1 to 7.5)		6.0 (4.3 to 7.7)
Tropical	5	31.8	33.6	0.6 (−0.8 to 1.9)		0.7 (−0.9 to 2.2)
NCA4 region
North east	298	26.1	31.8	12.0 (10.8 to 13.2)	<0.001	11.9 (10.8 to 12.9)	<0.001
Midwest	726	27.0	32.9	9.8 (8.9 to 10.8)		9.9 (9.0 to 10.7)
Northern great plains	226	26.4	34.0	9.6 (5.6 to 13.7)		9.6 (5.9 to 13.3)
South west	198	28.9	34.9	7.2 (5.6 to 8.8)		7.0 (5.5 to 8.4)
Southern great plains	401	32.7	38.5	6.8 (5.5 to 8.2)		7.4 (6.0 to 8.7)
North west	113	24.8	33.3	5.9 (2.4 to 9.5)		6.4 (2.8 to 10.1)
South east	977	30.8	34.8	4.3 (3.6 to 5.1)		5.3 (4.4 to 6.2)

On average across the US, extreme heat was at 34.4°C. Ambient temperature (°F)=(°C×9/5)+32.

^*Defined based on 95th centiles of the local county specific temperature distribution during the warm season.

^†Excess risks are expressed versus the local first centile.