Table 1.

Thermal characteristics of the source environment for each population listed in order of decreasing latitude (i.e., north to south). Values represent averages from 2000 – 2020, calculated from PRISM climate data at a 1 km buffer around the sampled tree hole. Seasonal temperature variation is defined as the difference between the mean warmest month temperature and the mean coolest month temperature. Warm-season maximum is defined as the mean daily maxima in the Spring and Summer. The # days > 35 or 31.6°C refer to the average number of days where the maximum temperatures exceeded the stated threshold, either across the year, or when considering only non-dormant periods (January – July) or adult activity periods (March – July). See Supplemental Figure S18 for correlations between temperatures variables and Supplemental Figure S19 for comparisons between the PRISM and iButton temperature estimates for the ‘SB’ and ‘POW’ populations.

Pop.	Annual mean temp. (°C)	Jan – March mean temp. (°C)	Seasonal temp. variation (°C)	Warm-season maximum (°C)	# days > 35°C		# days > 31.6°C
					Across year	Jan. - July	Across year	March - July
EUG	11.48	6.33	16.01	22.69	4.29	2.23	18.33	9.45
HOP	14.57	9.41	15.38	26.77	24.90	11.95	57.67	28.863
PLA	16.08	9.91	18.08	28.04	29.95	17.00	76.24	40.27
MAR2	14.24	10.31	11.62	24.77	8.71	4.18	25.95	12.81
MAR1	14.04	10.18	11.29	24.41	6.33	3.05	20.86	10.36
JRA	15.45	11.49	11.61	25.29	10.43	4.77	27.14	13.54
WAW	15.83	8.73	20.51	28.19	41.57	20.95	87.76	44.18
PAR	14.40	9.88	13.26	26.52	14.71	5.77	46.67	22.73
SB	16.44	11.82	13.51	27.86	26.81	11.77	59.95	29.72
POW	18.75	15.08	11.65	27.77	18.14	5.09	50.62	21.09