The Mission Viejo 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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34° on Nov. 17, 1958, the coldest reading for this week of the year since 1921. Next is 37° in 1938.
Mission Viejo’s center stands about 420 ft above sea level. Within three miles the land runs from 240 ft to 870 ft, a difference of 630 ft: hilly country. The highest named summit within 15 miles is Santiago Peak, about 5,660 ft, 11 miles northeast.
Under the town center the state geologic map shows Pliocene marine rocks (sandstone, mudstone), from the Miocene to Pleistocene, less than 23 million 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 4×. 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, mudstone. Age: Oligocene to Pliocene, 2.6 to 34 million years old. About 8 mi of the line.
Felsic-volcanic, mafic-volcanic. Age: Late Jurassic to Early Cretaceous, 100 to 164 million years old. About 4 mi of the line.
Sandstone, mudstone. Age: Miocene to Pleistocene, less than 23 million years old. About 3 mi of the line.
Sandstone, conglomerate. Age: Middle Eocene to Early Miocene, 16 to 48 million years old. About 2 mi of the line.
Mudstone, sandstone. Age: Paleocene to Oligocene, 23 to 66 million years old. About 2 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 0.8 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.
A raindrop that lands in Mission Viejo reaches the Pacific Ocean by way of Oso Creek, Trabuco Creek and San Juan Creek: about 11 river miles.
Often dry. About 100% of the way is mapped as streams that run only after rain or snowmelt; the water makes the whole trip in floods.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Mission Viejo; river miles along the main stem, rounded.
Mission Viejo has a cold semi-arid climate. Summer afternoons average 74° in September; winter nights fall to about 50° in January. About 9 inches of rain fall in a normal year.
On November 14 Mission Viejo normally reaches 69° and falls to 55°. The record high is 81°, in 1940; the record low 39°, in 1938. The most rain on this date, 1.11 in, fell in 1944.
Normals 1991–2020 and records since 1921 at Newport Beach Harbor, 12 miles west, 410 ft lower. NOAA, through RCC-ACIS.
