Peotone Weather

National Weather Service Forecast for: Peotone, IL Issued by: National Weather Service Chicago/Romeoville, IL

Updated: Sat, 29-Aug-2026 2:46am CDT

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Peotone, IL

Saturday Mostly Sunny Sunday Partly Sunny Monday Mostly Sunny Tuesday Mostly Sunny Wednesday Sunny Thursday Chance Showers And T-Storms then Slight Chance Showers And T-Storms Friday Chance Showers And T-Storms then Slight Chance Showers And T-Storms   Hi 80 °F Hi 86 °F Hi 90 °F Hi 91 °F Hi 91 °F Hi 87 °F Hi 86 °F   Overnight Partly Cloudy Saturday Night Slight Chance Rain Showers then Mostly Cloudy Sunday Night Partly Cloudy Monday Night Partly Cloudy Tuesday Night Partly Cloudy Wednesday Night Chance Showers And T-Storms Thursday Night Slight Chance Showers And T-Storms   Lo 60 °F Lo 66 °F Lo 69 °F Lo 72 °F Lo 72 °F Lo 70 °F Lo 67 °F

Forecast from NOAA-NWS for Peotone, IL.

071
FXUS63 KLOT 290700
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
200 AM CDT Sat Aug 29 2026

.KEY MESSAGES...

- Periodic showers and storms are possible through early next
  week, but many hours will remain dry

- Heat and humidity ramp up next week with highest heat indices
  expected mid-week

&&

.DISCUSSION...
Issued at 200 AM CDT Sat Aug 29 2026

Surface high pressure that has made for pleasant conditions the
past couple of days is slowly departing to the east. An upper
level ridge is expected to slowly slide eastward and expand
across the Great Plains today. There is a fairly stout MCS in
eastern South Dakota, on the east side of the ridge axis that is
slowly moving into southwestern Minnesota currently. The
northwest flow from the ridge that is presently overhead would
normally steer this system directly to Chicago; however, models
are suggesting a mid level wave to pass over the northern Plains
which will help flatten the ridge. This will effectively help
keep most of the better forcing to the north of the Wisconsin
stateline. Regional radar trends will be monitored through the
course of the day to ensure that no southern deviation occurs,
but there is one other fly in the ointment which will help
prevent concerns with rain/storm chances today: surface layer
dry air. Event the most aggressive models that have the system
making a southern shift and entering northern Illinois run into
issues with the dry air that is currently over the region and
shows the complex eroding away. For now, PoPs were constructed
limiting the chances to north of Interstate 88 this afternoon
into the early evening. There are certainly chances for
sprinkles as south of Interstate 80, but confidence is low that
they can make it to the surface through the dry air. With the
better forcing to the north, thunder is not currently forecasted
for this afternoon/evening time frame.

A slightly better short wave is expected to ride over top of
the ridge tomorrow night and Sunday morning. Forcing with this
wave will be slightly better over northern Illinois to provide
better confidence to increase PoPs (relative to Saturday
afternoon). Lapse rates look fairly poor leaving only narrow,
skinny CAPE depicted in model soundings. Thunder mention was
added to the forecast, but limited the probability to less than
25 percent as coverage is expected to be more isolated.

The previously mentioned upper level ridge will be responsible
for the weather for much of the week next week as it sits over
much of the CONUS. There is uncertainty in the exact placement
of the ridge, (more flat/southerly located = more
showers/storms; more amplified/centrally located = drier) to
merit confidence in timing and coverage through early next
week. No major changes deviated from the chance PoPs the NBM
provided. While periods of showers and storms will be possible,
the expectation is for far more drier times that wet.

Southwest flow will help advect warmer 850 mb temperatures
under the ridge through the week. Heat and humidity is expected
to slowly rise through week. Models have been consistently
showing highest heat index values (in the mid to upper 90s) by
the middle of the week. The GFS is notably warmer than the than
the Euro, so there is still some uncertainty on the exact heat
values, but there is gaining confidence in another hot stretch
of temperatures as we enter September.

At the end of the forecast time period, models are trying to
suggest that the ridge starts to break down and returns
northern Illinois to northwest flow overhead (which would aid
shower/storm development). The NBM is clearly picking up on
this signal with higher end chance PoPs into next weekend.
Timing at this distance is very fuzzy logic, but there may be
better chances for rain/storms late Friday or Saturday.

DK

&&

.AVIATION /06Z TAFS THROUGH 12Z SUNDAY/...
Issued at 1206 AM CDT Sat Aug 29 2026

A large surface high pressure system continues to serve as the
dominant influence on weather locally. Nearly calm winds
overnight will turn southwesterly after daybreak and increase
toward 10kt (with a few gusts up to 20kt) this afternoon. Clouds
will thicken first at FL200 before lowering toward FL100 this
afternoon in advance of a remnant sheared-out vort max. While
the vort max will pass directly overhead this afternoon and
evening, a resident dry low-level airmass should render largely
virga. Do think a few sprinkles may survive to the ground in the
20-00Z timeframe, but will withhold mention in the TAFs given no
expected impacts to operations.

The development of a 35-40kt southwesterly low-level jet
oriented into the Lower Great Lakes atop a developing broad
frontal boundary should encourage the development of rain
showers toward the very end of the TAF period. Will go ahead and
introduce PROB30 groups at ORD/MDW from 06-12Z (tomorrow).

Borchardt

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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