The Union City 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.
Partly cloudy
Showers likely
Showers likely
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Partly cloudy
34° on Nov. 14, 2022, the coldest reading for this week of the year since 1996. Next is 35° in 2024.
Union City’s center stands about 90 ft above sea level. Within three miles the land runs from 10 ft to 1,460 ft, a difference of 1,450 ft: steep hill country. The highest named summit within 15 miles is Mount Allison, about 2,640 ft, 11 miles southeast.
The section below crosses 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 10×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 9 mi of the line.
Siltstone-mudstone. Age: Early Cretaceous to Late Cretaceous, 66 to 145 million years old. About 6 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 2 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 2 mi of the line.
Sandstone, mudstone. Age: Oligocene to Pliocene, 2.6 to 34 million years old. About 0.9 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 Union City reaches San Francisco Bay and the Pacific Ocean by way of Alameda Creek and Coyote Hills Slough: about 7 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Union City; river miles along the main stem, rounded.
Union City has a warm-summer Mediterranean climate. Summer afternoons average 78° in July; winter nights fall to about 42° in January. About 16 inches of rain fall in a normal year.
On November 14 Union City normally reaches 65° and falls to 46°. The record high is 79°, in 2010; the record low 34°, in 2022. The most rain on this date, 0.51 in, fell in 2006.
Normals 1991–2020 and records since 1996 at Fremont, 4 miles south. NOAA, through RCC-ACIS.
