Table 1.

Linear Regression of cooling and heating degree-days from 1981 to 2018 for different base temperatures and weighting. Gradient (m) and intersection (c) of equation DD = m × Year + c, with R² and 95% confidence intervals.

	Area			Population
DD type	R2	m	c	R2	m	c
CDD 18	0.72	3.76 ± 0.88	−6496 ± 1753	0.90	9.55 ± 1.18	−17591 ± 2366
CDD 18.3	0.64	4.03 ± 1.13	−7087 ± 2262	0.90	9.41 ± 1.20	−17379 ± 2406
CDD 22	0.67	2.96 ± 0.79	−5407 ± 1573	0.85	6.00 ± 0.96	−11261 ± 1916
CDD 23	0.68	2.50 ± 0.64	−4595 ± 1289	0.83	5.04 ± 0.87	−9495 ± 1741
CDD 24	0.68	2.31 ± 0.60	−4316 ± 1204	0.80	4.21 ± 0.80	−7976 ± 1607
CDD 25	0.68	1.84 ± 0.48	−3440 ± 951	0.76	3.31 ± 0.70	−6284 ± 1405
HDD 10	0.61	−6.61 ± 2.01	16134 ± 4025	0.82	−6.20 ± 1.11	12919 ± 2211
HDD 15	0.66	−7.76 ± 2.12	19332 ± 4233	0.89	−9.85 ± 1.33	20634 ± 2651
HDD 15.5	0.66	−7.88 ± 2.13	19660 ± 4261	0.89	−10.27 ± 1.35	21527 ± 2689
HDD 16	0.66	−7.99 ± 2.15	19992 ± 4289	0.90	−10.70 ± 1.36	22438 ± 2728
HDD 17	0.67	−8.23 ± 2.18	20667 ± 4349	0.91	−11.57 ± 1.40	24303 ± 2809
HDD 18	0.68	−8.46 ± 2.21	21356 ± 4413	0.91	−12.46 ± 1.45	26215 ± 2894