Wetter Averages and Extremes for Chicago Area

The recent rains and associated flooding in the Chicago area are reflecting the long-term pattern of wetter conditions in the region. Here are a few samples of that pattern.

First of all, northeast Illinois (Cook and several surrounding counties – see map below) has experienced a shift in precipitation over the last 120 years. This plot shows the amounts for each year as green dots, and an 11-year running average showing longer periods of dry conditions (brown) and wet conditions (green). There is a pretty remarkable shift from a drier climate between 1895 and 1965 with lots of brown, towards a wetter climate from 1966 to present where green dominates.

If you compare the average annual precipitation between the two periods, you get 32.9 inches for the earlier period and 36.8 inches for the later period. That is a 3.9 inch increase, or about 12 percent.

If you look at the 10 wettest years in the record, 8 out of the 10 came after the shift in 1965. The two exceptions were 1902 at #1 and 1954 at #10.

Rank Year Precipitation
1 1902 48.02
2 1972 46.68
3 2008 45.95
4 1990 45.66
5 2009 45.40
6 1993 44.34
7 2011 43.12
8 1982 42.77
9 1970 42.76
10 1954 41.54

Of course, we have still experienced drought conditions in this later wet period, as noted in 2005 and 2012. However, the wetter years far outnumber the dry years since 1965. BTW, this pattern is not unique. I have seen this across the state.

northeast-il
Click to enlarge. Source http://www.southernclimate.org/products/trends.php

Here is the same plot for northeast Illinois for just the month of August. The green shading comes in a little later, showing generally wetter conditions since the 1980s. What is startling is the number of very wet Augusts in the last 50 years. The two wettest were 1987 with 10.04 inches and 2007 with 10.88 inches, which is more than double the long-term average.

As this plots show, the issue is not just a shift towards a wetter period over time but a shift towards wetter extremes as well.

As of August 27, 2014, the northeast region is at 5.4 inches, 1.83 inches above average.

northeast-il-aug
Click to update. Source http://www.southernclimate.org/products/trends.php

Here is the region used in this discussion (aka Climate Division 2). Climate divisions are regions of roughly similar climate. The advantages of a regional average are no missing data and increased statistical confidence in the resulting values. You can read more about them here.

northeast

Chicago Gets Soaked Again

Heavy rains fell across the Chicago metropolitan area again today (August 22, 2014). Here is the map of rainfall amounts from our volunteer CoCoRaHS network. You will get a slightly larger and more clear image if you click on the map below. Many sites in the orange have received the average August rainfall in just 1 day. The largest total so far is from an observer in Bloomingdale in DuPage County with 5.45 inches.

august22
Click to enlarge.

Here are the reports for the morning of August 22, 2014, ranked from high to low. Most observers report between 7 and 8 am.

Station ID Station Name Total Precip (inches)
 IL-DP-72 Bloomingdale 0.9 NNE 5.45
 IL-CK-12 Bridgeview 1.3 NNW 4.86
 IL-GY-2 Dwight 4.1 NNW 4.82
 IL-LE-18 Sublette 0.1 NNE 4.78
 IL-CK-88 Countryside 0.8 ENE 4.69
 IL-CK-211 Oak Lawn 1.6 WNW 4.68
 IL-LS-36 Marseilles 2.8 NW 4.67
 IL-CK-152 Chicago Ridge 0.2 WSW 4.51
 IL-DP-77 Roselle 1.1 W 4.46
 IL-CK-149 Oak Lawn 0.5 SSW 4.41
 IL-CK-154 Worth 0.1 E 4.29
 IL-GY-19 South Wilmington 0.3 WNW 4.15
 IL-DP-109 Elmhurst 0.8 ESE 4.10
 IL-LS-25 Marseilles 5.6 WNW 4.10
 IL-DP-14 Westmont 1.2 SSE 4.05
 IL-KK-23 Bonfield 4.0 WSW 3.92
 IL-CK-148 Oak Lawn 1.9 SE 3.73
 IL-KN-11 St Charles 1.1 SW 3.70
 IL-LV-14 Odell 4.4 SE 3.70
 IL-CK-75 Elk Grove Village 2.2 WSW 3.69
 IL-CK-98 La Grange Park 0.7 SSW 3.64
 IL-CK-187 North Riverside 0.4 W 3.61
 IL-CK-145 Oak Park 1.5 S 3.59
 IL-DP-117 Elmhurst 2.0 SE 3.57
 IL-DP-38 Elmhurst 0.4 SW 3.55
 IL-CK-63 Elk Grove Village 0.6 ESE 3.52
 IL-KN-50 Elburn 2.7 NNE 3.48
 IL-CK-131 Schaumburg 2.0 E 3.45
 IL-DP-100 Bartlett 1.1 SE 3.35
 IL-LS-47 Earlville 7.6 SSE 3.35
 IL-KN-30 Elburn 0.4 NW 3.32
 IL-LS-50 Seneca 1.2 NNE 3.30
 IL-CK-82 Burnham-Hegewisch 1.6 NNW 3.19
 IL-LS-45 Streator 1.3 WSW 3.19
 IL-KN-63 Geneva 1.7 WSW 3.15
 IL-DP-85 Villa Park 1.0 NW 3.13
 IL-CK-61 Oak Park 1.0 SW 3.11
 IL-WF-19 Washburn 5.2 W 3.10
 IL-DP-29 Glen Ellyn 1.6 SSE 3.02
 IL-LS-51 Seneca 1.1 NNE 3.00
 IL-LV-17 Emington 2.2 SSE 3.00
 IL-LV-12 Streator 1.4 S 2.99
 IL-KN-62 Batavia 1.3 WNW 2.97
 IL-KN-58 Lily Lake 2.1 E 2.95
 IL-CK-202 River Forest 0.9 SSE 2.93
 IL-GY-9 Mazon 0.5 ENE 2.88
 IL-CK-240 Chicago 2.7 WNW 2.87
 IL-DP-79 Burr Ridge 1.9 SW 2.87
 IL-LS-17 Ottawa 1.6 N 2.82
 IL-CK-129 Schaumburg 2.7 WSW 2.81
 IL-KN-8 Geneva 3.3 WSW 2.81
 IL-LS-1 Ottawa 1.3 NW 2.78
 IL-DP-18 Downers Grove 2.1 SE 2.66
 IL-DP-40 Lombard 1.0 NNW 2.62
 IL-DP-98 Downers Grove 0.9 S 2.60
 IL-CK-192 Park Ridge 0.7 WNW 2.57
 IL-GY-12 Braceville 0.5 SSE 2.54
 IL-DP-63 Bartlett 1.0 SSE 2.51
 IL-KN-5 Batavia 0.7 WSW 2.44
 IL-CK-153 Alsip 0.2 E 2.42
 IL-CK-238 Elmwood Park 0.7 NNW 2.42
 IL-LS-49 North Utica 6.3 N 2.35
 IL-KN-78 Geneva 1.3 SSW 2.34
 IL-KN-104 Geneva 3.9 WSW 2.33
 IL-LE-14 Amboy 0.5 ESE 2.33
 IL-KN-79 Geneva 1.6 WSW 2.23
 IL-DP-49 Naperville 2.5 ESE 2.22
 IL-CK-180 Park Ridge 0.5 SSW 2.21
 IL-DP-32 Lisle 1.3 SE 2.16
 IL-CK-178 Rolling Meadows 0.9 ESE 2.15
 IL-DP-122 Clarendon Hills 0.5 NW 2.14
 IL-LS-39 Ottawa 0.5 NNW 2.14
 IL-KN-67 St. Charles 6.0 NW 2.13
 IL-KN-33 North Aurora 1.5 NE 2.12
 IL-KN-64 St. Charles 0.1 E 2.12
 IL-DK-21 De Kalb 0.6 SE 2.09
 IL-DP-118 Darien 0.4 SSE 2.09
 IL-DP-83 Lombard 1.2 NNW 2.05
 IL-CK-74 Oak Park 1.3 NNE 2.04
 IL-MCH-49 Cary 0.3 NE 2.04
 IL-DP-96 Lombard 1.0 WSW 2.02
 IL-LS-27 Oglesby 0.6 ESE 1.94
 IL-WF-12 Germantown Hills 1.3 NW 1.93
 IL-CK-121 Palatine 1.3 E 1.92
 IL-LS-34 La Salle 0.1 W 1.90
 IL-LV-7 Chatsworth 0.4 ESE 1.85
 IL-DK-10 Malta 0.4 SSE 1.84
 IL-CK-81 Arlington Heights 1.8 NNW 1.83
 IL-DP-42 Carol Stream 0.3 SSE 1.83
 IL-DP-69 Glen Ellyn 1.0 NE 1.81
 IL-DP-16 Aurora 3.6 SE 1.80
 IL-CK-107 Evanston 1.4 N 1.79
 IL-LS-2 Oglesby 0.4 N 1.79
 IL-CK-14 Chicago 5.5 ESE 1.78
 IL-CK-243 Elmwood Park 0.7 ESE 1.77
 IL-LS-12 Peru 0.6 SW 1.76
 IL-CK-32 Chicago 6.4 NNE 1.75
 IL-CK-175 Winnetka 1.2 S 1.75
 IL-WL-118 Elwood 4.6 NE 1.72
 IL-CK-235 Park Ridge 1.1 ENE 1.70
 IL-DP-101 Aurora 3.8 SE 1.66
 IL-PR-9 Dunlap 2.6 S 1.57
 IL-CK-106 Hoffman Estates 4.6 W 1.56
 IL-LS-46 Mendota 2.4 SE 1.56
 IL-KN-9 Elgin 1.0 S 1.54
 IL-KN-95 Elgin 2.5 W 1.53
 IL-IR-10 Buckley 0.2 SSE 1.52
 IL-CK-168 Ravenswood Manor 0.1 ESE 1.49
 IL-WL-119 Homer Glen 1.6 NW 1.47
 IL-DP-27 Naperville 2.1 ESE 1.45
 IL-WL-46 Peotone 0.4 ENE 1.45
 IL-KN-2 Elgin 2.3 WNW 1.39
 IL-WL-67 Channahon 2.5 SSE 1.38
 IL-KD-23 Montgomery 1.7 SSE 1.37
 IL-LV-10 Pontiac 0.7 ESE 1.37
 IL-WL-61 Channahon 0.8 NNE 1.37
 IL-WL-71 Plainfield 1.1 SW 1.37
 IL-CK-50 Palos Park 1.3 SW 1.35
 IL-KN-51 Sugar Grove 1.4 ENE 1.32
 IL-WL-25 Crete 2.6 E 1.32
 IL-WL-41 Peotone 0.5 ENE 1.32
 IL-LV-6 Pontiac 1.0 SE 1.31
 IL-MCH-43 Algonquin 0.7 N 1.31
 IL-KD-34 Plainfield 4.8 SW 1.30
 IL-WL-84 Beecher 3.4 ENE 1.30
 IL-WL-99 Manhattan 1.9 SE 1.29
 IL-DP-102 Bolingbrook 2.7 NE 1.28
 IL-WL-20 Manhattan 4.7 ENE 1.28
 IL-WL-79 Peotone 0.5 SE 1.27
 IL-CK-215 Glenview 0.9 SW 1.26
 IL-WL-93 New Lenox 4.2 SE 1.26
 IL-GY-20 Morris 2.5 SSE 1.25
 IL-WL-121 Monee 4.9 W 1.25
 IL-WN-19 Rockton 1.0 ESE 1.24
 IL-WL-36 Homer Glen 3.9 WNW 1.22
 IL-CK-206 Park Forest 1.0 SW 1.21
 IL-KN-107 South Elgin 0.9 WSW 1.20
 IL-SP-7 Davis 0.5 N 1.17
 IL-LK-39 Riverwoods 0.4 ENE 1.14
 IL-WL-104 Plainfield 2.7 SE 1.14
 IL-LK-25 Lincolnshire 1.3 WSW 1.13
 IL-KD-46 Oswego 1.0 SW 1.10
 IL-SP-18 Freeport 0.9 ESE 1.10
 IL-WL-16 Homer Glen 0.8 ENE 1.07
 IL-WL-51 Plainfield 2.4 SSE 1.06
 IL-FD-9 Gibson 3.0 WNW 1.05
 IL-WL-80 Lockport 1.3 SE 1.05
 IL-WL-100 Joliet 2.9 WNW 1.05
 IL-KD-5 Montgomery 0.8 SSE 1.04
 IL-WL-120 Joliet 1.2 W 1.04
 IL-KX-11 Galesburg 8.8 S 1.03
 IL-WL-82 Orland Park 4.6 WNW 1.03
 IL-HY-6 New Windsor 2.0 N 1.02
 IL-LK-16 Buffalo Grove 1.5 N 1.02
 IL-WL-64 Joliet 2.3 WNW 1.02
 IL-GY-10 Minooka 0.3 NE 1.01
 IL-CK-146 Glenwood 1.5 ESE 1.00
 IL-KN-82 Batavia 0.8 S 1.00
 IL-LS-7 Sheridan 3.4 SSE 1.00
 IL-LK-69 Highwood 0.9 S 0.99
 IL-CK-53 Glencoe 0.1 NW 0.98
 IL-CK-94 Lincolnwood 1.8 E 0.98
 IL-MCH-66 Harvard 2.8 SSE 0.97
 IL-FL-9 London Mills 1.4 SE 0.95
 IL-WL-111 New Lenox 1.0 NE 0.95
 IL-WF-14 El Paso 5.2 NNW 0.95
 IL-KX-9 Knoxville 0.7 NW 0.93
 IL-MCH-13 Bull Valley 2.5 WNW 0.92
 IL-KK-25 Bonfield 4.2 NNE 0.91
 IL-WL-50 Lockport 3.3 ESE 0.91
 IL-KD-24 Oswego 5.0 SSE 0.90
 IL-KN-91 Hampshire 0.7 W 0.89
 IL-DP-57 Aurora 3.5 NE 0.88
 IL-GY-4 Coal City 0.4 N 0.87
 IL-GY-16 Morris 6.4 ESE 0.87
 IL-WL-73 Wilmington 2.6 SE 0.86
 IL-MCH-61 Woodstock 1.5 WSW 0.84
 IL-WL-97 New Lenox 3.3 E 0.84
 IL-LK-11 Lincolnshire 0.9 N 0.83
 IL-GY-21 Coal City 2.8 N 0.82
 IL-WL-103 Joliet 1.8 NNE 0.80
 IL-CK-42 Mount Prospect 3.0 NE 0.79
 IL-LK-53 Lakemoor 1.5 SE 0.78
 IL-WL-108 Plainfield 4.1 NW 0.78
 IL-LK-15 Bannockburn 0.5 ESE 0.77
 IL-TZ-14 Morton 1.0 SSE 0.77
 IL-KK-28 Chebanse 0.4 NNE 0.76
 IL-WL-123 Bolingbrook 1.4 W 0.76
 IL-CK-232 Lincolnwood 3.2 E 0.75
 IL-GY-1 Carbon Hill 3.1 N 0.75
 IL-LV-4 Chenoa 3.9 NNW 0.75
 IL-TZ-1 Morton 1.0 S 0.74
 IL-WN-30 Pecatonica 2.3 S 0.74
 IL-KN-86 Elgin 7.5 WSW 0.72
 IL-LK-9 Lake Villa 1.1 SSW 0.72
 IL-LE-8 Ashton 0.4 SSW 0.71
 IL-LK-74 Mundelein 1.6 WNW 0.70
 IL-WL-72 New Lenox 2.9 ENE 0.69
 IL-LK-22 Lake Forest 2.1 NNE 0.68
 IL-MCD-5 Macomb 0.6 WNW 0.68
 IL-LK-70 Fox Lake 2.4 SE 0.67
 IL-WL-105 Plainfield 2.9 NNW 0.65
 IL-DP-75 Naperville 1.1 NW 0.64
 IL-MCH-59 Harvard 0.3 E 0.64
 IL-SP-6 Freeport 2.0 NW 0.64
 IL-WN-2 Roscoe 1.6 ESE 0.64
 IL-LK-54 Mundelein 0.5 NNE 0.62
 IL-MR-4 Aledo 0.4 NE 0.62
 IL-LK-86 Mundelein 1.8 NW 0.60
 IL-LK-13 Lake Bluff 1.3 W 0.59
 IL-MCL-2 Arrowsmith 1.7 NNE 0.59
 IL-MR-6 Aledo 0.4 NE 0.59
 IL-BU-8 Tiskilwa 2.1 N 0.58
 IL-DK-17 De Kalb 1.8 NNE 0.58
 IL-BN-14 Capron 0.1 N 0.57
 IL-KK-26 Kankakee 3.2 SE 0.55
 IL-CK-197 Orland Hills 0.6 SE 0.53
 IL-LK-42 Gurnee 1.6 W 0.53
 IL-LK-83 Antioch 3.4 WSW 0.53
 IL-WD-5 Morrison 3.2 E 0.53
 IL-LK-29 Lake Bluff 1.4 W 0.51
 IL-SP-8 Winslow 4.3 ESE 0.51
 IL-WD-14 Sterling 4.9 WSW 0.51
 IL-WL-63 New Lenox 1.8 SE 0.51
 IL-MCL-9 Danvers 1.7 WNW 0.50
 IL-SP-14 Freeport 1.7 ESE 0.50
 IL-DK-5 Cortland 0.3 SSW 0.49
 IL-MCH-33 Woodstock 3.8 SW 0.48
 IL-MCH-52 Woodstock 0.8 SSW 0.47
 IL-LK-3 Beach Park 1.4 W 0.45
 IL-LK-19 Waukegan 2.2 N 0.45
 IL-TZ-10 Tremont 3.6 E 0.45
 IL-LK-72 Wadsworth 1.4 SSE 0.44
 IL-MCL-23 Normal 1.9 ESE 0.44
 IL-IR-14 Watseka 6.9 WNW 0.43
 IL-OG-4 Byron 3.2 N 0.43
 IL-WN-14 Rockford 3.3 NE 0.43
 IL-BU-5 Princeton 1.1 SE 0.42
 IL-BU-9 La Moille 0.2 NNE 0.42
 IL-CK-64 Homewood 0.1 ESE 0.42
 IL-LK-8 Gurnee 2.5 NE 0.42
 IL-LK-84 Waukegan 1.7 E 0.40
 IL-LE-10 Dixon 3.0 NNW 0.39
 IL-WF-18 El Paso 6.2 SW 0.39
 IL-CK-170 Flossmoor 0.5 SW 0.38
 IL-HY-1 Orion 4.1 NW 0.38
 IL-MCL-18 Bloomington 3.2 NE 0.36
 IL-LE-5 Sterling 4.3 NE 0.35
 IL-MCL-17 Bloomington 2.7 NE 0.35
 IL-CR-11 Milledgeville 0.4 ESE 0.34
 IL-DP-78 Naperville 2.4 SE 0.34
 IL-MCL-32 Danvers 0.34
 IL-WN-8 Rockford 0.7 NW 0.34
 IL-KD-12 Yorkville 1.1 W 0.33
 IL-WL-113 New Lenox 2.1 SE 0.33
 IL-KK-34 Bradley 1.1 SW 0.32
 IL-WD-8 Coleta 1.4 SSW 0.32
 IL-IR-2 Ashkum 5.6 E 0.31
 IL-RI-10 Moline 1.1 N 0.31
 IL-CP-81 Dewey 1.6 NNW 0.30
 IL-LK-23 Winthrop Harbor 0.2 SSE 0.30
 IL-SP-17 Pearl City 0.4 SW 0.30
 IL-KK-22 Bourbonnais 1.5 NNE 0.29
 IL-KD-25 Yorkville 1.8 SSE 0.27
 IL-LK-27 Winthrop Harbor 0.7 SSW 0.27
 IL-LE-17 Dixon 1.5 SW 0.27
 IL-RI-3 Moline 0.9 N 0.27
 IL-RI-13 Moline 0.7 NNE 0.26
 IL-CR-12 Mount Carroll 6.8 NNW 0.25
 IL-HY-4 Atkinson 2.6 NNE 0.25
 IL-HY-8 Geneseo 2.0 NW 0.25
 IL-LG-32 Lincoln 2.7 NNE 0.22
 IL-OG-12 Davis Junction 1.1 SW 0.22
 IL-KD-7 Plano 0.4 NNE 0.20
 IL-WN-26 Rockford 1.5 ENE 0.20
 IL-KK-35 Bourbonnais 2.9 E 0.19
 IL-MCD-7 Colchester 3.5 NE 0.19

Dryness Across Northern and Central Illinois

After a wet start to the 2014 growing season, we have seen a significant drop in rainfall across parts of northern and central Illinois in the last few weeks. Here is the 30-day rainfall as a percent of average. Areas in the orange are 25 to 75 percent of average while the areas in red are less than 25 percent of average. There are reports of soil moisture running low in some areas. On the other hand, southern Illinois has received above-average rainfall in the last 30 days.

IL-prcp-mpe-030-pct-20140818

Besides the switch from too wet to too dry in northern and central Illinois, and too much rain in southern Illinois, the other issue is that temperatures have been running about 4 degrees below average for the past 30 days. We are getting some heat this week. However, the longer-term forecasts indicate a return to cooler temperatures and more rain after this week through September 1.

If you look at the last 90 days the heavier rains in June and early July masks the recent dryness (map below). In fact, at the 90 day time scale rainfall in Illinois is generally at or above long-term average (1981-2010), as denoted by the grays and greens. This is one of the challenges of drought monitoring – sorting out short-term dryness versus long-term wetness or vice versa.

IL-prcp-mpe-090-pct-20140818

 

Champaign-Urbana Illinois Gets Soaked

Heavy rains fell over Champaign-Urbana, Illinois on Saturday with more rain early Sunday morning. The two-day total through Sunday morning was 4.42 inches at the official NWS COOP station at the Illinois State Water Survey near the corner of First and Windsor in Champaign. Here is the breakdown by day, with the official observation time at 8 am:

  • 0.09 inches of rain by 8 am July 12
  • 4.33 inches of rain by 8 am July 13

The 4.33 inches for July 13, 2014, at the official, long-term site for Champaign-Urbana, falls short of the historical record 1-day total, which is 5.32 inches of rain from August 12, 1993.

Here are the reports from the CoCoRaHS network for Champaign-Urbana, showing two reports of over 5 inches, and several reports of between 4 and 5 inches.

GetMap

Here is a wider view showing the rains of the last two days from a NWS product that combines radar and rain gage information. The amounts of 2.5 to 4 inches stretches from Chicago down to east-central Illinois with the heaviest amounts of possibly up to 6 inches in Champaign, Piatt, McLean, and Ford counties.

july13-mpe