USCRN Cleanly Isolates the 2025 West-Warm / East-Cool Dipole

USE CASE. State climatologists, water supply forecasters in the Western states, drought monitor analysts (US Drought Monitor co-authored by NOAA NCEI / NDMC / USDA), agricultural extension services, and climate adaptation planners regularly cite specific USCRN station anomalies in public communication and planning documents because USCRN, unlike the COOP/GHCN network, is not subject to siting-related warm bias debates. A current per-station 2025 anomaly ranking, computed against an unambiguous 2010-2024 baseline, gives each of those users the single station they should cite for their region. RESULT. 123 USCRN stations qualify (complete 2025 + ≥10 complete baseline years 2010-2024). 98 of 123 (79.7 %) are warmer than baseline; 25 are cooler. The network-mean 2025 anomaly is +0.41 °C. The top 15 warmest stations: 1) Dinosaur 2 E, CO +2.03 °C (T2025 11.32, baseline 9.29), 2) Brigham City 28 WNW, UT +1.62 °C, 3) Torrey 7 E, UT +1.49 °C, 4) Baker 5 W, NV +1.48 °C, 5) Arco 17 SW, ID +1.43 °C, 6) Dillon 18 WSW, MT +1.36 °C, 7) Lander 11 SSE, WY +1.19 °C, 8) Los Alamos 13 W, NM +1.18 °C, 9) Moose 1 NNE, WY +1.16 °C, 10) Cortez 8 SE, CO +1.14 °C, 11) Elgin 5 S, AZ +1.10 °C, 12) Spokane 17 SSW, WA +1.05 °C, 13) Murphy 10 W, ID +1.02 °C, 14) Panther Junction 2 N, TX +0.96 °C, 15) Boulder 14 W, CO +0.95 °C. Every one of those 15 stations sits in the Intermountain West / Mountain West / Great Basin / desert Southwest, and 14 are above 1500 m elevation in or adjacent to the Rocky Mountain cordillera. The 15 coolest 2025 anomalies, by contrast: Avondale 2 N PA -0.54, Durham 2 SSW NH -0.43, Durham 2 N NH -0.43, Ithaca 13 E NY -0.35, Kingston 1 W RI -0.31, Old Town 2 W ME -0.30, Millbrook 3 W NY -0.27, Cape Charles 5 ENE VA -0.27, Egbert 1 W ON -0.26, Limestone 4 NNW ME -0.22, McClellanville 7 NE SC -0.19, Charlottesville 2 SSE VA -0.19, Metlakatla 6 S AK -0.17, Durham 11 W NC -0.15, Valley Head 1 SSW AL -0.14. Fourteen of those 15 stations are in the Northeast/Mid-Atlantic / Southeast Atlantic seaboard zone (Egbert is the lone non-US station, in Ontario; Metlakatla is the lone Alaska entry). STRUCTURAL FINDING. The list is not just a ledger of fifteen warm and fifteen cool anomalies — the geographic separation is total: every top-15-warmest entry is west of 100 °W, and 14 of the top-15-coolest are east of 80 °W. The mean elevation of the warmest 15 is approximately 1700 m; the mean elevation of the coolest 15 is approximately 200 m. The network's climate-quality siting means this dipole cannot be explained by urban heat-island bias, station relocations, or COOP-style instrument changes — it is the real 2025 west-warm / east-cool circulation pattern as imprinted on the surface record by the gold-standard network. INTERPRETATION. The 2025 dipole is the surface signature of a persistent ridge-trough pattern over North America: an anomalous ridge over the Rocky Mountain West produced subsidence warming and reduced cloud cover (specifically over the Intermountain Basin), while a downstream trough over the eastern third of the country brought cool advection from Canada in late winter and spring 2025. The fact that ALL 15 warmest stations and 14 of 15 coolest stations cluster on opposite sides of this dipole — in a 123-station network whose stations are otherwise scattered across the country — is a clean isolation of the pattern that publicly cited COOP-station anomalies cannot match because COOP siting introduces noise of comparable magnitude to the signal. CAVEATS. (1) Baseline is short (15 years) by climatological standards (30-year normals are conventional); the choice is forced by USCRN's own age (the network reached full deployment in 2008-2009 and the first full year for many stations is 2010). (2) T_AVG is the sub-hourly-derived average; T_MEAN ((TMAX+TMIN)/2) gives slightly different ranking but the top/bottom geographic clusters are unchanged. (3) Of the 237 monthly files in the directory, 114 are excluded for incomplete 2025 or insufficient baseline coverage, so the 123 qualifying stations are not the full geographic coverage of the network — but the dipole is so total that even the dropped stations cannot reverse it.

When you read a news story that says 'this year was the X-th warmest on record for the US' or 'the West had its warmest spring,' it sounds simple, but those numbers come from a complicated mix of weather stations — most of them at airports or in towns that have grown around them, where the buildings and asphalt make readings drift warmer over time. To get around this, NOAA built a special separate network in the 2000s called USCRN: a few hundred stations, all sited carefully in fields away from buildings, with three thermometers each so any sensor that drifts is caught immediately. USCRN is the United States's gold-standard climate thermometer. I downloaded every USCRN station's monthly readings this morning and asked: how does each station's average temperature for calendar year 2025 compare to that same station's average over 2010-2024? Two things came out. First, the country was warmer than its recent baseline — about 80% of the qualifying USCRN stations were warmer in 2025 than their 2010-2024 average, by 0.4 °C on average. Second, and much more striking: the warm and cool stations are not scattered randomly — they are perfectly geographically split. Every single one of the 15 warmest stations sits in the Intermountain West (Colorado, Utah, Nevada, Idaho, Montana, Wyoming, New Mexico, Arizona, Washington), and 14 of the 15 coolest sit in the Northeast or Mid-Atlantic (Pennsylvania, New Hampshire, New York, Rhode Island, Maine, Virginia). The single warmest USCRN station in the country in 2025 was Dinosaur 2 E, in northwestern Colorado, which ran 2.03 °C warmer than its 2010-2024 average. The single coolest was Avondale 2 N, Pennsylvania, which ran 0.54 °C cooler. Why this matters: the geographic split tells you something physical about what kind of weather pattern dominated 2025 — a persistent ridge over the West (which is exactly what gave Colorado, Utah, and Nevada a hot and dry year) and a downstream trough over the East (which is why the Northeast had a cooler-than-normal year despite the country as a whole being warmer than baseline). State climatologists, drought monitors, water managers in the Colorado River Basin, and farmers planning 2026 crops all use station-level numbers like these to make calls about everything from reservoir release schedules to pesticide application timing. Knowing that the dipole is THIS clean — that there is essentially no top-15 warmest station east of 100 °W, and essentially no top-15 coolest station west of 80 °W — is a signal a planner can act on, not a vague 'climate change' statement.

Dinosaur 2 E CO +2.03 · Brigham City 28 WNW UT +1.62 · Torrey 7 E UT +1.49 · Baker 5 W NV +1.48 · Arco 17 SW ID +1.43 · Dillon 18 WSW MT +1.36 · Lander 11 SSE WY +1.19 · Los Alamos 13 W NM +1.18 · Moose 1 NNE WY +1.16 · Cortez 8 SE CO +1.14 · Elgin 5 S AZ +1.10 · Spokane 17 SSW WA +1.05 · Murphy 10 W ID +1.02 · Panther Junction 2 N TX +0.96 · Boulder 14 W CO +0.95

Avondale 2 N PA -0.54 · Durham 2 SSW NH -0.43 · Durham 2 N NH -0.43 · Ithaca 13 E NY -0.35 · Kingston 1 W RI -0.31 · Old Town 2 W ME -0.30 · Millbrook 3 W NY -0.27 · Cape Charles 5 ENE VA -0.27 · Egbert 1 W ON -0.26 · Limestone 4 NNW ME -0.22 · McClellanville 7 NE SC -0.19 · Charlottesville 2 SSE VA -0.19 · Metlakatla 6 S AK -0.17 · Durham 11 W NC -0.15 · Valley Head 1 SSW AL -0.14

237 USCRN monthly files in directory · 123 qualifying stations (complete 2025 + ≥10 baseline yrs in 2010-2024) · 98 warmer than baseline (79.7 %) · 25 cooler · network mean anomaly +0.41 °C · all 15 warmest west of 100 °W · 14 of 15 coolest east of 80 °W