Climate twins of St. Helena, CA
These are the US cities whose 12-month climate pattern most closely matches St. Helena'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. Helena vs its climate twin
Top match: Sonora, CA
| Month | St. Helena | Sonora | ||||
|---|---|---|---|---|---|---|
| High | Low | Precip | High | Low | Precip | |
| January | 58.8°F | 40.2°F | 6.47 in | 55.7°F | 32.8°F | 6.32 in |
| February | 62.5°F | 41.9°F | 6.71 in | 58.2°F | 34.2°F | 5.50 in |
| March | 66.8°F | 43.9°F | 4.98 in | 62.1°F | 37.0°F | 5.37 in |
| April | 71.8°F | 46.3°F | 1.97 in | 66.7°F | 39.7°F | 3.03 in |
| May | 78.1°F | 50.5°F | 1.31 in | 75.6°F | 45.5°F | 1.54 in |
| June | 85.4°F | 54.2°F | 0.35 in | 85.3°F | 50.8°F | 0.34 in |
| July | 88.7°F | 56.0°F | 0.01 in | 92.8°F | 56.8°F | 0.03 in |
| August | 88.8°F | 55.7°F | 0.04 in | 91.9°F | 55.5°F | 0.07 in |
| September | 86.6°F | 53.8°F | 0.06 in | 86.7°F | 50.8°F | 0.20 in |
| October | 78.1°F | 49.4°F | 1.65 in | 76.2°F | 43.0°F | 1.64 in |
| November | 65.8°F | 43.7°F | 3.24 in | 63.2°F | 36.4°F | 3.24 in |
| December | 58.3°F | 39.6°F | 7.18 in | 55.1°F | 32.4°F | 5.51 in |
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 →