The Sumas plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
Chance of showers
Showers likely
Showers likely
Mostly sunny
Mostly cloudy
Partly cloudy
Partly cloudy
6.59 inches of rain fell in two days, the most for this week of the year since records began in 1903. The next wettest, 4.28 inches, fell in 1910.
Sumas’s center stands about 40 ft above sea level. Within three miles the land runs from 20 ft to 600 ft, a difference of 580 ft: hilly country. The highest named summit within 15 miles is Kaisoots Mountain, about 5,440 ft, 14 miles east.
Under the town center the state geologic map shows Alluvium (silt, sand), from the Holocene, less than 12,000 years old.
The section below crosses 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 5×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Fine-detrital, coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 9 mi of the line.
Silt, sand. Age: Holocene, less than 12,000 years old. About 5 mi of the line.
Graywacke. Age: Late Devonian to Cretaceous, 66 to 384 million years old. About 3 mi of the line.
Metasedimentary. Age: Devonian to Permian, 273 to 422 million years old. About 3 mi of the line.
Fine-detrital, coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 3 mi of the line.
Fine-detrital, coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 2 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 1 smaller unit along the line are not listed.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.
Sumas has a warm-summer Mediterranean climate. Summer afternoons average 77° in August; winter nights fall to about 32° in January. A normal year brings about 11 inches of snow; with the rain, that comes to about 50 inches of water.
On November 14 Sumas normally reaches 49° and falls to 36°. The record high is 64°, in 1953; the record low 9°, in 1955. The most rain on this date, 3.42 in, fell in 2021.
Normals 1991–2020 and records since 1903 at Clearbrook, 3 miles southwest. NOAA, through RCC-ACIS.
