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Shaded-relief map of Cortland, Illinois: rivers, roads, the city limits and where the water drains.
ILLINOIS · DEKALB COUNTY

Cortland

4,592 people, 900 ft above sea level in DeKalb County.

900 ftElevation, city center
4,592People, 2024 estimate
4 sq miLand area
Sunny 46°
Sunny now Dew point 26° · NW 8 mph · high 44°
City of Cortland River Interstate 2 miles
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The Cortland 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.

MILE1
TODAY

Today in Cortland

NWS forecast and National Blend of Models · updated 2:00 PM CST
RIGHT NOW Greater Rockford Airport (KRFD) · 2:54 PM
Sunny
46° Sunny Feels like 42° · high of 44° near 3 PM
WindNW 8 mphno gusts
Humidity45%rising to 100% by morning
Pressure30.28 in →steady
Visibility10 mihaze-free
CloudsClear
UV index—no forecast
Dew point 26° · Dry35° by Tuesday: more humid
DryComfortableStickyMuggyOppressive
NEXT RAIN
Showers
Friday30% chance · showers
LIKELY AMOUNT—amounts come within 3 days
LAST RAINNov. 120.01 in · 2 dry days
ALERTS & OUTLOOKS
No watches or warnings for DeKalb County
NWS Chicago and the Storm Prediction Center · checked 3:16 PM
SUN & MOON
↑ 6:43 AM4:35 PM ↓
9 h 52 m of daylight, 2 minutes less than yesterday
Waxing crescent, 25% lit. Next full moon: Nov. 24.
AIR & POLLEN
11
GOODAir quality index · fine particles
Tomorrow: None, moderate. No pollen source yet.

The next three days, hour by hour

Sky: clear, cloudy, night Rain likely National Blend of Models
SATURDAY, NOV. 14
SUNDAY, NOV. 15
MONDAY, NOV. 16
TUESDAY, NOV. 17
3p
6p
9p
Mid
3a
6a
9a
Noon
3p
6p
9p
Mid
3a
6a
9a
Noon
3p
6p
9p
Mid
3a
6a
9a
Noon
clear day
clear night
clear night
mostly clear night
partly cloudy night
partly cloudy day
mostly sunny
clear day
clear day
clear night
mostly clear night
mostly clear night
mostly clear night
mostly sunny
mostly sunny
mostly sunny
mostly sunny
mostly clear night
clear night
clear night
mostly clear night
mostly sunny
mostly sunny
mostly sunny
TEMPERATURE °F
44°
25°
47°
26°
49°
32°
CHANCE OF RAIN
50%
WIND, MPH
5
0
0
0
0
0
0
0
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1
5
9
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HOW IT FEELS · DEW POINT
Dry: dew points 24 to 35°

The next seven days, and how sure we are

Forecast, with the range 8 in 10 ensemble members agree on Normal, about 48° / 31°
SAT Nov. 14 Sunny Sunny
44° 23°
0% rain — NW 6 A
SUN Nov. 15 Mostly sunny Mostly sunny
49° 23°
0% rain — N 0 A
MON Nov. 16 Mostly sunny Mostly sunny
52° 29°
0% rain — SW 6 A
TUE Nov. 17 Mostly sunny Mostly sunny
55° 33°
0% rain — S 8 A
WED Nov. 18 Partly cloudy Partly cloudy
56° 43°
10% rain — S 12 B
THU Nov. 19 Partly cloudy Partly cloudy
59° 41°
20% rain — WSW 7 B
FRI Nov. 20 Chance of showers Chance of showers
60° 47°
30% rain up to 0.05″ SSE 8 C
How sure are we? AModels agree: highs within 4° BSome spread: within 8° CWide spread: check back
Range from the National Blend of Models percentiles · graded on Forecast Scores
AIR MAIL

Where today’s air came from

The air arriving over Cortland about 5,000 feet above the ground was over the Gulf of Alaska three days ago, and over the northern Plains a day ago, about 2,700 miles back along its path. It came down from about 12,800 feet up, warming and drying as it sank. Near the ground the air came from British Columbia; at 10,000 feet, from the northern Rockies. It feels dry all the same. Traced back 72 hours through NOAA’s hourly RAP analyses and the GFS beyond them, nine paths at each of three heights.

THIS WEEK, FOUR YEARS AGO Nov. 11, 2022

The hottest this week has been

74° on Nov. 11, 2022, the hottest reading for this week of the year since 1966. Next is 73° in 1989.

73°
74°
19892022
Source: NOAA RCC-ACIS, the De Kalb record since 1966.
MILE2
THE GROUND

What Cortland stands on

Cortland’s center stands about 900 ft above sea level. Within three miles the land runs from 840 ft to 910 ft, a difference of 70 ft: gently rolling country.

Under the town center the state geologic map shows Maquoketa Formation or Group (shale, limestone), from the Late Ordovician, 445 to 454 million years old.

The section below crosses 2 rock units mapped at the surface.

Hinckley to Kingston, cut in half

A section south to north, 24 miles through the town center
700 ft800 ft900 ft CORTLAND900 ftLow point730 ft ← S · HinckleyKingston · N →

Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.

Rock at the surface along the line

Maquoketa Formation or Group

Shale, limestone. Age: Late Ordovician, 445 to 454 million years old. About 16 mi of the line.

Galena Group (Trenton Limestone)

Dolostone, limestone. Age: Late Ordovician, 447 to 459 million years old. About 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.

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.

MILE3
THE WATER

Where Cortland’s rain goes

A raindrop that lands in Cortland reaches the Gulf of America by way of the East Branch South Branch Kishwaukee, the South Branch Kishwaukee, the Kishwaukee, the Rock River and the Mississippi: about 1,640 river miles.

THE WAY DOWN, TO SCALE
Cortland≈ 1,640 mi · the Gulf of America
FROM THE CENTER OF CORTLAND ≈ 1,640 mi to the Gulf of America East Branch South Branch Kishwaukee → South Branch Kishwaukee → Kishwaukee → Rock River → Mississippi

Traced down the USGS NHDPlus V2.1 river network from the Census center point of Cortland; river miles along the main stem, rounded.

MILE5
THE ALMANAC

Cortland’s year

1991–2020 normals · records since 1966 · De Kalb, 5 mi west-northwest

Cortland has a hot-summer humid continental climate. Summer afternoons average 83° in July; winter nights fall to about 13° in January. A normal year brings about 33 inches of snow; with the rain, that comes to about 37 inches of water.

28°13°33°17°45°27°59°37°70°49°80°60°83°63°81°61°75°53°62°41°46°30°34°19° JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDEC 1234 TODAY CORTLAND 37.2 in rain and snowmelt
Normal high to low, by month Record high to low, by day Rain by month Freezing
July, average83° / 63°high / low, the warmest month
January, average28° / 13°high / low, the coldest month
Rain and melted snow37.2 inwettest months: May and June
Snow a year33.1 insnowiest: January
Hottest on record103°FAugust 17, 1988
Coldest on record−27°FJanuary 20, 1985
Wettest day on record8.09 inJuly 18, 1996
Snowiest day on record15.7 inFebruary 2, 2011
90° days a year13very few reach 100°
Nights at or below 32°141and 56 days that stay below freezing
Climate typeHot-summer humid continentalKöppen Dfa

AROUND THE RING

1Freeze seasonfrom the first fall freeze, about Oct. 16, to the last in spring, about April 19 (median dates)
2Highs below freezingDec. 19 to Feb. 15; normal highs stay below 32°
3Lows below freezingNov. 8 to April 2; normal lows fall below 32°
4Wettest stretchMay through July: 13.4 of the year’s 37.2 inches
NOVEMBER 14 IN THE RECORD

On November 14 Cortland normally reaches 47° and falls to 30°. The record high is 73°, in 1999; the record low 2°, in 1986. The most rain on this date, 0.34 in, fell in 1994.

MONTH BY MONTH
JanFebMarAprMayJunJulAugSepOctNovDec
Normal high28°33°45°59°70°80°83°81°75°62°46°34°
Normal low13°17°27°37°49°60°63°61°53°41°30°19°
Rain and melt, in1.691.712.243.564.794.574.004.063.322.962.312.04
Snow, inches10.28.74.41.30.00.00.00.00.00.11.86.6
Record high63° (1967)75° (2024)84° (1986)92° (1986)96° (2018)101° (1988)102° (1995)103° (1988)95° (2026)89° (2025)76° (2016)69° (2012)
Record low−27° (1985)−26° (2019)−13° (2002)8° (1982)24° (1989)34° (1993)43° (1967)39° (1986)27° (1991)13° (1988)−8° (1976)−22° (1983)

Normals 1991–2020 and records since 1966 at De Kalb, 5 miles west-northwest. NOAA, through RCC-ACIS.

MILE7
ON THE NETWORK

Around Cortland on the Forecast Network

Neighboring plates

Aurora IL · 24 MI 24 miles southeast Naperville IL · 30 MI 30 miles southeast Chicago IL · 52 MI 52 miles east Milwaukee WI · 86 MI 86 miles northeast Madison WI · 88 MI 88 miles northwest Indianapolis IN · 200 MI 200 miles southeast
FORECASTCITY
Map of Cortland, Illinois. Explore the plate
ILLINOIS · DEKALB

Cortland

4,592 people, 900 ft above sea level in DeKalb County.

900 ftElevation
4,592People
4 sq miLand
Sunny 46°
SunnyDew point 26°
1

Today in Cortland

NEXT 15 HOURS
Now clear day 44° 0%
6p clear night 37° 0%
9p clear night 31° 0%
12a mostly clear night 28° 0%
3a partly cloudy night 26° 0%
6a partly cloudy night 25° 0%
Showers
NEXT RAINFriday · 30%
→
Sat0%
Sunny Sunny
23
44
A
Sun0%
Mostly sunny Mostly sunny
23
49
A
Mon0%
Mostly sunny Mostly sunny
29
52
A
Tue0%
Mostly sunny Mostly sunny
33
55
A
Wed10%
Partly cloudy Partly cloudy
43
56
B
Thu20%
Partly cloudy Partly cloudy
41
59
B
Fri30%
Chance of showers Chance of showers
47
60
C
Letters show how sure the forecast is: A, models agree; B, some spread; C, check back. Sample data.
THIS WEEK, FOUR YEARS AGO · NOV. 11, 2022

74°, the hottest this week of the year has been since 1966.

2

What Cortland stands on

Cortland’s center stands about 900 ft above sea level. Within three miles the land runs from 840 ft to 910 ft, a difference of 70 ft: gently rolling country.

Cortland, south to north Cortland900 ft ← SN → 24 miles through the town center; vertical exaggeration about 122×. Colors: rock at the surface.
Elevation, center900 ft
Within 3 miles840 to 910 ft
Lie of the landGently rolling (70 ft of relief)
Rock at the surfaceMaquoketa Formation or Group
Its ageLate Ordovician, 445 to 454 million years old
5

Cortland’s year

Cortland has a hot-summer humid continental climate. Summer afternoons average 83° in July; winter nights fall to about 13° in January. A normal year brings about 33 inches of snow; with the rain, that comes to about 37 inches of water.

JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDEC 1234 37.2 in
July, average83° / 63° · high / low, the warmest month
January, average28° / 13° · high / low, the coldest month
Rain and melted snow37.2 in · wettest months: May and June
Snow a year33.1 in · snowiest: January
Hottest on record103°F · August 17, 1988
Coldest on record−27°F · January 20, 1985
Wettest day on record8.09 in · July 18, 1996
Snowiest day on record15.7 in · February 2, 2011
90° days a year13 · very few reach 100°
Nights at or below 32°141 · and 56 days that stay below freezing
Climate typeHot-summer humid continental · Köppen Dfa
1Freeze season · from the first fall freeze, about Oct. 16, to the last in spring, about April 19 (median dates)
2Highs below freezing · Dec. 19 to Feb. 15; normal highs stay below 32°
3Lows below freezing · Nov. 8 to April 2; normal lows fall below 32°
4Wettest stretch · May through July: 13.4 of the year’s 37.2 inches
NOVEMBER 14 IN THE RECORD

On November 14 Cortland normally reaches 47° and falls to 30°. The record high is 73°, in 1999; the record low 2°, in 1986. The most rain on this date, 0.34 in, fell in 1994.

Normals 1991–2020 and records since 1966 at De Kalb, 5 miles west-northwest. NOAA, through RCC-ACIS.
3

Where the rain goes

≈ 1,640 mito the Gulf of AmericaEast Branch South Branch Kishwaukee → South Branch Kishwaukee → Kishwaukee → Rock River → Mississippi

A raindrop that lands in Cortland reaches the Gulf of America by way of the East Branch South Branch Kishwaukee, the South Branch Kishwaukee, the Kishwaukee, the Rock River and the Mississippi: about 1,640 river miles.