June Weather Summary

Overview
June 2014 was a month that featured well above normal rainfall for much of central Illinois, and seasonable temperatures for all of central and southeast Illinois.  Only a couple rounds of Canadian air affected the region this month, on June 4-5 and 10-14, when highs were mainly limited to the 70s.  Aside from these days, highs were consistently in the mid to upper 80s, with several days reaching the lower 90s.  This resulted in monthly mean temperatures near to slightly above normal.  The main weather story for the month was an active storm pattern.  The more significant and widespread severe weather events and locally heavy rain affected the region on June 3rd-4th, 21st, 23rd, and 30th.  The most frequent bouts of heavy rain affected central and northern Illinois, where monthly precipitation totals were 1.5 to 2 times normal.  Several sites reported monthly rain totals which ranked in their top 5 wettest June on record.  These include Decatur (3rd wettest - 9.93"), Jacksonville (3rd wettest - 10.18"), Peoria (9.67" - 2nd wettest), and Springfield (8.87" - 5th wettest).

As mentioned above, several episodes of strong to severe storms and heavy rain occurred during the month.   Summaries of the more significant events are below. 

  • June 3-4 (Tuesday night into Wednesday morning)
    A large complex of thunderstorms tracked through central and southeast Illinois during the night of June 3rd into the morning of June 4th.  The storms initially developed in a highly unstable airmass across South Dakota and Nebraska during the afternoon of the 3rd, then moved southeastward along a stationary frontal boundary extending from northern Missouri into the central sections of Illinois and Indiana.  Due to the high degree of instability and low-level wind shear in place across the Plains, the storms quickly became severe, producing numerous reports of very large hail and even a few tornadoes across Nebraska during the afternoon and early evening.  The cells gradually merged into a much larger complex of showers and thunderstorms as the entire system followed the front toward the Mississippi River later in the evening.  By the time the storms crossed into west-central Illinois around midnight, the threat for large hail and tornadoes had waned considerably as the primary storm mode now supported damaging wind gusts and heavy rainfall.  A few bow echoes embedded within the complex produced wind gusts of 60 to 65 mph as the system tracked through central Illinois.  Most notably, wind damage was reported in Jacksonville, in Latham in southern Logan County, and near Clinton in DeWitt County.  In addition to the sporadic wind damage, a widespread 1 to 2-inch rainfall occurred across the area.  A few locations in Springfield picked up between 3 and 3.25 rainfall in a short period of time, leading to flash flooding of several viaducts and underpasses.  The storms continued southeastward through the night and eventually exited into Indiana by mid-morning on June 4th.

  • June 21 (Saturday afternoon into early evening)
    Clusters of strong to locally severe thunderstorms affected portions of central Illinois.  This convection was largely driven by a mid-level disturbance resulting from a large thunderstorm complex over the Plains the previous night, in combination with high instability during peak heating during the afternoon.  The storms primarily affected areas between the I-74 and I-72 corridors, with large hail up to golf ball size, and isolated damaging wind gusts of 55-65 mph.

  • June 23 (Monday afternoon and evening)
    A slow moving frontal boundary and weak upper level wave interacted with a very moist airmass to produce heavy rain over portions of central and southeast Illinois Monday afternoon and night.  The heaviest rains fell in a corridor from around Springfield northeast to Danville and Hoopeston, where some areas received 2 to 4 inches.  In a narrow corridor across east central Champaign and west central Vermilion Counties, radar estimated 4 to 6 inches fell, and an observer within this corridor at St. Joseph reported 4.83 inches.  The image below shows the radar estimated rainfall amounts ending at 7 am Tuesday.  The purple areas represent at least 2.5 inches of rain, with the darker blue estimating at least 4 inches.

  • June 30 (Monday morning and evening)
    Isolated reports of severe weather were received on Monday, June 30th, while many areas of north-central Illinois experienced locally heavy rainfall thanks to two rounds of convection.  The first round of thunderstorms occurred during the pre-dawn areas along and north of the I-74 corridor.  These storms produced prolific lightning, heavy rainfall, and gusty winds before they moved further southeastward and dissipated by mid-morning.  As the day progressed, the atmosphere across central Illinois became highly unstable with Convective Available Potential Energy (CAPE) values exceeding 4000J/kg.  Despite the very unstable airmass, a layer of warm air aloft kept the atmosphere "capped" and didn't allow convection to form.  Further north where the cap was weaker or non-existent, thunderstorms were able to develop along an old outflow boundary and track eastward across Iowa into north-central Illinois.  Most of this activity remained focused along the I-80 corridor during the afternoon and evening, resulting in widespread heavy rainfall and flash flooding.  As an upper-level wave approached, thunderstorms were eventually able to develop further south and west along a new outflow boundary from central Illinois westward into Missouri by late evening.  A few of these storms produced gusty winds and brief heavy downpours before slowly dissipating as they dropped toward the I-70 corridor.  Rainfall totals were highest along a Cedar Rapids, Iowa...to Pontiac...to Danville line.  Many areas across eastern Iowa into north-central Illinois picked up 3 to 4 inches of rain...with localized amounts as high as 5 to 6 inches from Cedar Rapids southeastward to near Henry.  Further south, rainfall totals decreased substantially...with less than one quarter of an inch being reported south of I-70. 

 

 Temperature and Precipitation Maps

 

 

 

  June Temp. Departure from normal

June Precip. Total

June Precip. % of normal 

 

Climate Data

The table below summarizes June 2014 precipitation and temperature, and departure from normal for selected cities across central and southeast Illinois.  Data from Peoria and Springfield are from ASOS sites, while others are from NWS Cooperative Observers.
 

Site Precipitation Departure from Normal Average Temp. Departure from Normal
Charleston

7.37" 

 +3.02"

 77.9

 +4.8
Decatur

9.93" 

 +4.50"

 72.6

  -0.7
Galesburg

6.81" 

 +2.51"

 72.2 

 +1.1 
Jacksonville

10.18" 

 +5.60" 

 73.4

 +2.2
Lincoln

6.42" 

 +2.10" 

 72.4

 +0.3

Normal

6.94" 

 +3.03"

 72.1

 +0.7
Olney

4.21" 

 +0.02"

 74.0

 +0.6
Peoria

9.67" 

 +6.14"

 74.5

 +2.7
Springfield

8.87" 

 +4.41"

 75.0

 +2.5
Urbana

8.19" 

 +3.85"

 73.0 

 +0.8


Links below are the monthly climate summaries for area cities. Only the summaries for Peoria, Springfield and Lincoln are considered "official", meaning they are the station of record for their respective locations. The other summaries are "supplemental", meaning another location in the area is the official climate station for that city.

Climate data for other area cities is available at http://www.nws.noaa.gov/climate/xmacis.php?wfo=ilx

 



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