Climate twins of St. Charles, ID

These are the US cities whose 12-month climate pattern most closely matches St. Charles's. Each "twin" must be at least 140 miles away to avoid trivial near-neighbor matches. Similarity is computed across all 24 monthly metrics (12 average temperatures + 12 average precipitations), normalized so temperature and precipitation contribute equally.

Side-by-side: St. Charles vs its climate twin

Top match: Rock River, WY

Month	St. Charles			Rock River
	High	Low	Precip	High	Low	Precip
January	28.7°F	7.5°F	0.80 in	31.3°F	10.3°F	0.41 in
February	31.4°F	7.8°F	0.82 in	34.8°F	11.5°F	0.63 in
March	40.4°F	17.8°F	0.83 in	45.6°F	18.1°F	0.72 in
April	50.4°F	28.6°F	1.09 in	55.1°F	25.0°F	1.38 in
May	60.5°F	37.8°F	1.80 in	64.8°F	33.3°F	1.74 in
June	71.3°F	44.9°F	0.92 in	77.4°F	42.6°F	1.38 in
July	81.0°F	51.0°F	0.57 in	85.3°F	48.3°F	1.11 in
August	79.9°F	48.0°F	0.76 in	83.0°F	45.9°F	0.82 in
September	70.0°F	39.2°F	1.09 in	73.6°F	36.3°F	0.96 in
October	55.8°F	29.7°F	1.10 in	59.1°F	26.7°F	1.01 in
November	40.8°F	20.1°F	0.76 in	42.8°F	17.6°F	0.55 in
December	30.4°F	10.4°F	0.75 in	32.8°F	10.7°F	0.49 in

Cities that consider St. Charles their climate twin

These US cities have St. Charles in their top 3 most-similar list — meaning if you were to move from any of these places, St. Charles would feel familiar.

Medicine Bow, WY (ranks St. Charles #2)
Rock River, WY (ranks St. Charles #2)

How this is computed

Each city is represented by a 24-dimensional vector: 12 monthly average temperatures and 12 monthly average precipitations. Each dimension is z-score normalized across the population of US cities, so that temperature variance and precipitation variance contribute proportionally. Distance between cities is Euclidean. We filter out cities within 2° latitude/longitude (~140 miles) so that "twins" mean climatically similar but geographically distinct — not just the neighboring town. Full methodology →