The Grand Isle 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
Mostly cloudy
Mostly cloudy
Mostly sunny
Mostly sunny
Partly cloudy
Partly cloudy
1° on Nov. 13, 2019, the coldest reading for this week of the year since 1945. Next is 10° in 1986.
Grand Isle’s center stands about 170 ft above sea level. Within three miles the land runs from 90 ft to 240 ft, a difference of 150 ft: gently rolling country. The highest named summit within 15 miles is Georgia Mountain, about 1,440 ft, 12 miles east-southeast.
Under the town center the state geologic map shows Stony Point Formation (shale, limestone), from the Late Ordovician, 445 to 459 million years old.
The section below crosses 10 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 16×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Slate. Age: Cambrian to Early Ordovician, 471 to 542 million years old. About 4 mi of the line.
Dolostone, limestone. Age: Early Ordovician, 471 to 487 million years old. About 3 mi of the line.
Shale, limestone. Age: Late Ordovician, 445 to 459 million years old. About 3 mi of the line.
Dolostone. Age: Early Cambrian, 521 to 542 million years old. About 2 mi of the line.
Unconsolidated. Age: Quaternary, less than 2.6 million years old. About 2 mi of the line.
Argillite. Age: Middle Ordovician, 459 to 471 million years old. About 1 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 4 smaller units 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 Grand Isle reaches the St. Lawrence River by way of Lake Champlain and the Richelieu: about 110 river miles. The St. Lawrence carries it on to the Atlantic.
Lake on the way: Lake Champlain.
80 miles of the trip are on the Richelieu.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Grand Isle; river miles along the main stem, rounded.
Grand Isle has a warm-summer humid continental climate. Summer afternoons average 81° in July; winter nights fall to about 10° in January. About 31 inches of rain fall in a normal year.
On November 14 Grand Isle normally reaches 46° and falls to 29°. The record high is 64°, in 1959; the record low 11°, in 2019. The most rain on this date, 0.88 in, fell in 2009.
Normals 1991–2020 and records since 1945 from the Plattsburgh Area threaded record (Plattsburgh International Airport, 10 miles southwest). NOAA, through RCC-ACIS.
