Decatur, Illinois 7 Day Weather Forecast
Wx Forecast - Wx Discussion - Wx Aviation
|
NWS Forecast for Decatur IL
National Weather Service Forecast for:
Decatur IL
Issued by: National Weather Service Lincoln, IL |
Updated: 2:09 pm CDT Aug 12, 2025 |
|
This Afternoon
 T-storms Likely
|
Tonight
 T-storms Likely then Slight Chance T-storms
|
Wednesday
 Partly Sunny
|
Wednesday Night
 Mostly Clear
|
Thursday
 Sunny
|
Thursday Night
 Mostly Clear
|
Friday
 Sunny
|
Friday Night
 Mostly Clear
|
Saturday
 Sunny
|
Hi 89 °F |
Lo 70 °F |
Hi 85 °F |
Lo 64 °F |
Hi 85 °F |
Lo 64 °F |
Hi 90 °F |
Lo 70 °F |
Hi 94 °F |
|
Hazardous Weather Outlook
This Afternoon
|
Showers and thunderstorms likely, mainly after 4pm. Partly sunny, with a high near 89. Southwest wind around 9 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms. |
Tonight
|
Showers and thunderstorms likely, mainly before 11pm. Mostly cloudy, with a low around 70. Southwest wind around 6 mph becoming calm in the evening. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms. |
Wednesday
|
Partly sunny, with a high near 85. North northwest wind 3 to 7 mph. |
Wednesday Night
|
Mostly clear, with a low around 64. North wind around 6 mph becoming calm in the evening. |
Thursday
|
Sunny, with a high near 85. Light east northeast wind. |
Thursday Night
|
Mostly clear, with a low around 64. Calm wind. |
Friday
|
Sunny, with a high near 90. Light and variable wind becoming southeast around 5 mph. |
Friday Night
|
Mostly clear, with a low around 70. |
Saturday
|
Sunny, with a high near 94. |
Saturday Night
|
Mostly clear, with a low around 72. |
Sunday
|
Sunny and hot, with a high near 95. |
Sunday Night
|
Mostly clear, with a low around 73. |
Monday
|
Mostly sunny, with a high near 93. |
Forecast from NOAA-NWS
for Decatur IL.
|
Weather Forecast Discussion
278
FXUS63 KILX 121913
AFDILX
Area Forecast Discussion
National Weather Service Lincoln IL
213 PM CDT Tue Aug 12 2025
.KEY MESSAGES...
- Scattered to numerous thunderstorms will continue through this
evening near and east of I-55, with chances shifting into
southeast Illinois on Wednesday.
- Seasonal conditions will be in place through Thursday. Hot and
humid weather returns Friday through the weekend. Heat indices
of 100 to 105 degrees appear likely.
&&
.DISCUSSION...
Issued at 213 PM CDT Tue Aug 12 2025
...Scattered Storms Through Wednesday, Then Drying Out...
Surface analysis early this afternoon shows a slow moving cold front
positioned from southern Wisconsin into eastern Iowa. The front is
expected to spread east into central Illinois overnight as an upper
trough swings into the Great Lakes Region. Looking at the finer
details, a remnant outflow boundary from an overnight MCS is
draped from near Lexington southward toward Springfield and has
been the focus for thunderstorm activity so far today. SPC
mesoanalysis as of 2 pm shows widespread SBCAPE of 2500+ J/kg
with an axis along the outflow boundary closer to 4000 J/kg. With
this amount of instability, storms are expected to develop very
quickly. This paired with slow storm motions and PWATs nearing 2
inches will lead to pockets of very heavy rain and perhaps some
localized flooding especially in urban areas. Although shear is on
the weaker side (<25 kts), a few of the strongest storms could
pose a threat for damaging downburst winds and small hail.
Scattered to numerous thunderstorms will continue this afternoon
with chances shifting into eastern Illinois by this evening.
The upper trough axis will shift further east-northeast into Quebec
Wednesday morning with the cold front sagging further southward into
southeast Illinois. Precipitation chances will be much lower on
Wednesday and confined to areas south of I-70 where a few storms
could fire during the afternoon hours. Precipitation will
dissolve by Wednesday night as the front dips further south
outside of the forecast area.
Drier conditions will be in place the next several days. A few
overnight MCS`s look to track through the Northern Plains/Upper
Mississippi Valley late this week through the weekend, but this
activity will largely stay north of here. Our next best chance for
rain returns early next week as a front drops into the area.
...Seasonal Temperatures Through Thursday, Then Turning Hot...
The pattern begins to shift late this week as a series of upper
waves attempt to break down the upper ridge over the western US. The
ridge will flatten some and shift eastward into the central US by
late in the week. Seasonal temperatures will be in place for just a
couple days before the ridge amplifies and mid-level heights rise
locally, bringing the return of hot and humid weather for the
weekend. Highs Friday through Sunday look to peak in the upper 80s
to low 90s, with heat indices upwards of 100-105 degrees.
The heat looks to be short-lived with temperatures returning back to
near normal by the early parts of next week as a few ridge riders
slide into the southern Great Lakes Region, ultimately lowering mid-
level heights and allowing the upper ridge to build back westward.
NMA
&&
.AVIATION... (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1226 PM CDT Tue Aug 12 2025
Scattered thunderstorms are likely (60% chance) to develop this
afternoon across the regional terminals ahead of a front. We have
therefore added a TEMPO group for TSRA, shifting from west to
east, between 20z-02z. Storm coverage and attendant cloud cover
will diminish late this evening as the front drops south of the
regional terminals. Winds will become light with a west component
overnight into Wednesday.
MJA
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
View a Different U.S. Forecast Discussion Location
(In alphabetical order by state)
|
|
|
|