The Ontario 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.
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−3° on Nov. 17, 2014, the coldest reading for this week of the year since 1931. Next is 2° in 1955.
Ontario’s center stands about 2,150 ft above sea level. Within three miles the land runs from 2,130 ft to 2,250 ft, a difference of 120 ft: gently rolling country. The highest named summit within 15 miles is Vale Butte, about 3,130 ft, 12 miles west-southwest.
Under the town center the state geologic map shows Alluvial deposits (sand, gravel, silt), from the Holocene, less than 12,000 years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 22×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone, siltstone, mudstone. Age: Miocene to Pliocene, 2.6 to 23 million years old. About 9 mi of the line.
Coarse-detrital, fine-detrital. Age: Pleistocene to Holocene, less than 33,000 years old. About 8 mi of the line.
Sand, gravel, silt. Age: Holocene, less than 12,000 years old. About 5 mi of the line.
Gravel, sand, silt. Age: Quaternary, less than 2.6 million years old. About 3 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
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.
A raindrop that lands in Ontario reaches the Pacific Ocean by way of the Stewart Carter Ditch, the Snake and the Columbia: about 690 river miles.
Lakes on the way: Lake Umatilla, Brownlee Reservoir and Hells Canyon Reservoir.
240 miles of the trip are on the Snake.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Ontario; river miles along the main stem, rounded.
Ontario has a cold semi-arid climate. Summer afternoons average 95° in July; winter nights fall to about 24° in January. About 10 inches of rain fall in a normal year.
On November 14 Ontario normally reaches 50° and falls to 30°. The record high is 65°, in 1953; the record low 7°, in 1978. The most rain on this date, 0.58 in, fell in 1965.
Normals 1991–2020 and records since 1931 from the Ontario Area threaded record (Ontario, 2 miles west-southwest). NOAA, through RCC-ACIS.
