ChescoWx Snow Climatology
Average Seasonal Snowfall Across Chester County
1991–2020 normal · every human snow observer, compared storm by storm
County average (area-weighted)
26.4"
1991–2020 normal · 26.4–28.0" depending on observers used
Snowiest areas
32"
northern ridges: Warwick / French Creek, Nantmeal
Least snow
21"
far south: Landenberg / London Britain
North vs south
29" / 23"
north of 40.1°N vs south of 39.85°N
Elevation effect
+32%
more snow per 1,000 ft (same storms)
How much snow does the county really get? Weighting every part of the county by its
area gives 26.4" a season (1991–2020) using every human observer; dropping the CoCoRaHS gauges, which mostly read low in the
same storms, gives 27.5"; COOP stations alone give 28.0". The published county season median for the same years is
27.8", so it already sits at the upper end of that range. Two things make the county feel snowier than its average:
the northern half of the county — where most long-record and gold-standard observers live — averages about
29–30" while the south averages about 23"; and 1991–2020 was a less snowy era —
over the full record (1890s on) every number here runs about 9% higher (county ≈ 29–30").
Observing sites used — estimated 1991–2020 seasonal average
| Site | Type | Elev ft | Storms | Season avg (in.) |
|---|---|---|---|---|
| EAST NANTMEAL | COOP / observer | 679 | 93 | 37.3 |
| ELVERSON (spotter) | Spotter site | 657 | 18 | 33.7 |
| DEVAULT 1W | COOP / observer | 409 | 158 | 33.6 |
| CHESTERBROOK (spotter) | Spotter site | 167 | 13 | 33.5 |
| POTTSTOWN (NWS report) | Other NWS report | 288 | 13 | 33.0 |
| COATESVILLE 2W | COOP / observer | 608 | 110 | 32.2 |
| PHOENIXVILLE (spotter) | Spotter site | 104 | 13 | 32.0 |
| THORNDALE | COOP / observer | 316 | 25 | 31.1 |
| SADSBURYVILLE | COOP / observer | 674 | 42 | 30.2 |
| SPRING CITY 2WSW | COOP / observer | 252 | 14 | 29.7 |
| 2 SE EXTON (spotter) | Spotter site | 516 | 8 | 29.4 |
| COATESVILLE | COOP / observer | 626 | 19 | 29.3 |
| GEIGERTOWN | COOP / observer | 431 | 112 | 29.1 |
| DOWNINGTOWN (spotter) | Spotter site | 240 | 36 | 28.7 |
| HOPEWELL | COOP / observer | 598 | 86 | 28.4 |
| WEST CALN (spotter) | Spotter site | 622 | 39 | 28.3 |
| EAST COVENTRY (spotter) | Spotter site | 177 | 34 | 28.1 |
| EXTON | COOP / observer | 309 | 45 | 27.9 |
| LANDENBERG (spotter) | Spotter site | 370 | 8 | 27.8 |
| GLENMOORE | COOP / observer | 614 | 297 | 27.7 |
| MORGANTOWN | COOP / observer | 598 | 129 | 27.6 |
| COATESVILLE 1SW | COOP / observer | 536 | 316 | 27.5 |
| DOWNINGTOWN 1.7 NE (CoCoRaHS) | CoCoRaHS | 310 | 12 | 27.4 |
| SPRING CITY (NWS report) | Other NWS report | 151 | 8 | 27.3 |
| HONEY BROOK 2SSE | COOP / observer | 704 | 222 | 27.1 |
| WEST CHESTER 2W | COOP / observer | 215 | 12 | 27.1 |
| WEST GROVE | COOP / observer | 418 | 122 | 27.0 |
| EXTON 2.1 SE (CoCoRaHS) | CoCoRaHS | 532 | 18 | 26.4 |
| SPRING CITY 0.6 SSW (CoCoRaHS) | CoCoRaHS | 217 | 12 | 26.4 |
| POTTSTOWN | COOP / observer | 160 | 146 | 26.3 |
| 1 NE EAST VINCENT TWP (NWS report) | Other NWS report | 252 | 9 | 26.2 |
| OXFORD 2.1 ENE (CoCoRaHS) | CoCoRaHS | 431 | 17 | 26.2 |
| WEST CHESTER 2NW | COOP / observer | 306 | 372 | 26.1 |
| WEST CHESTER (spotter) | Spotter site | 421 | 45 | 25.9 |
| VALLEY FORGE (NWS report) | Other NWS report | 263 | 16 | 25.3 |
| OCTORARO LAKE | COOP / observer | 324 | 116 | 25.3 |
| WEST CHESTER 1.8 SE (CoCoRaHS) | CoCoRaHS | 438 | 39 | 25.2 |
| POTTSTOWN 3.0 SSE (CoCoRaHS) | CoCoRaHS | 245 | 10 | 24.8 |
| EXTON (spotter) | Spotter site | 313 | 53 | 24.5 |
| WEST CHESTER 2.4 SSE (CoCoRaHS) | CoCoRaHS | 328 | 69 | 24.5 |
| ATGLEN 0.2 W (CoCoRaHS) | CoCoRaHS | 496 | 8 | 24.4 |
| BERWYN 0.7 WNW (CoCoRaHS) | CoCoRaHS | 540 | 15 | 24.3 |
| KENNETT SQUARE | COOP / observer | 403 | 62 | 24.2 |
| GLENMOORE (spotter) | Spotter site | 455 | 38 | 24.0 |
| NOTTINGHAM 1.5 SW (CoCoRaHS) | CoCoRaHS | 424 | 62 | 23.6 |
| OXFORD (spotter) | Spotter site | 564 | 9 | 23.1 |
| WEST GROVE 2.5 NNW (CoCoRaHS) | CoCoRaHS | 529 | 11 | 23.0 |
| UNIONVILLE 2.2 NE (CoCoRaHS) | CoCoRaHS | 320 | 27 | 22.1 |
| POTTSTOWN 5.9 SSW (CoCoRaHS) | CoCoRaHS | 288 | 16 | 22.0 |
| WESTTOWN | COOP / observer | 279 | 34 | 21.8 |
| PHOENIXVILLE 2.9 W (CoCoRaHS) | CoCoRaHS | 178 | 10 | 21.7 |
| CHADDS FORD 3.1 SW (CoCoRaHS) | CoCoRaHS | 350 | 46 | 21.3 |
| KENNETT SQUARE 4.1 NNE (CoCoRaHS) | CoCoRaHS | 358 | 29 | 20.3 |
| WEST GROVE 2.6 W (CoCoRaHS) | CoCoRaHS | 528 | 46 | 20.2 |
| WICKERTON 0.4 NW (CoCoRaHS) | CoCoRaHS | 392 | 29 | 17.5 |
| NEW LONDON (spotter) | Spotter site | 469 | 10 | 16.7 |
How the map is built. (1) Same-storm comparison: every human snow report in the county storm file (storms with a
county median of 2"+ and 4+ reports; reports the snow rules exclude are dropped) is fitted as site × storm, which measures how much
snow each site gets relative to the others in the same storms — so sites from different decades can be compared fairly.
56 sites with 8+ storms are used; Phoenixville 1E, Chadds Ford 2NE and Coatesville 1E (excluded from all snow statistics) and the
automated DEOS sites are left out. (2) Inches: those relative factors are scaled to the 1991–2020 normal with the 17 long-record
stations that have 10+ complete seasons, using a season-by-season model (station × season) so each station's normal is adjusted to the
same 30 winters. (3) Between sites: a trend in elevation (USGS 3DEP terrain, ~400 m grid, lightly smoothed) and latitude, plus the
sites' own departures from that trend spread over ~7 km. Leave-one-out check: a site's value is predicted within 2.9"
on average without using that site. Values at labelled dots are the site estimates; the shading is the smoothed surface, so a single
hilltop (East Nantmeal, 37") can sit above the shading around it. Raw observations, not homogenized; CoCoRaHS and spotter sites cover
recent winters only.
Source: Chester County Area climate stations — actual raw NWS COOP / FAA / Climate Reference Network / Delaware Environmental Observing System / NWS Trained Skywarn Program Observer CHPA-174 · terrain: USGS 3DEP
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