The Hillsborough 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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79° on Nov. 15, 2008, the hottest reading for this week of the year since 1945. Next is 78° in 2010.
Hillsborough’s center stands about 310 ft above sea level. Within three miles the land runs from 0 ft to 1,130 ft, a difference of 1,130 ft: steep hill country. Open water lies within three miles. The highest named summit within 15 miles is Morena Sierra, about 2,450 ft, 12 miles south-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 29×. 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: Jurassic to Cretaceous, 66 to 202 million years old. About 6 mi of the line.
Melange. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 6 mi of the line.
Sandstone, mudstone. Age: Miocene to Pleistocene, less than 23 million years old. About 4 mi of the line.
Greenstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 3 mi of the line.
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.
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 Hillsborough reaches San Francisco Bay and the Pacific Ocean by way of Sanchez Creek: about 1 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Hillsborough; river miles along the main stem, rounded.
Hillsborough has a warm-summer Mediterranean climate. Summer afternoons average 75° in September; winter nights fall to about 44° in January. About 20 inches of rain fall in a normal year.
On November 14 Hillsborough normally reaches 65° and falls to 49°. The record high is 78°, in 2008; the record low 36°, in 1978. The most rain on this date, 1.04 in, fell in 1968.
Normals 1991–2020 and records since 1945 from the San Francisco Airport Area threaded record (San Francisco International Airport, 3 miles north-northeast, 300 ft lower). NOAA, through RCC-ACIS.
