Excessive Heat in Wisconsin, July 20 to 22, 2016

Name: Excessive Heat in Wisconsin, July 20 to 22, 2016
Start: 2016-07-20T13:00
End: 2016-07-22T19:00
Location: Wisconsin

July 20 to 22, 2016 · NWS MPX · 6 events in 6 counties and zones

A large dome of high pressure that was centered across the mid section of the nation the week of July 18th, caused temperatures to rise into the 80s and 90s across the state. These temperatures combined with very high dew points in the mid to upper 70s, created heat indices between 100-110 degrees during the afternoon of Wednesday July 20th, and into Friday afternoon, July 22nd over portions of…

Where it happened

Every event with a place to put it; 6 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.

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The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 6

Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.

What happened

The episode as NWS MPX wrote it up.

A frontal boundary aiding in pooling of dew points and associated higher heat indices during this time period, especially along the St. Croix and Mississippi River Valley.

The highest heat indices occurred between 12 noon and 7 pm. However, even the overnight temperatures only fell into the upper 70s to lower 80s, creating dangerous readings for those who did not have air conditioning or were caught out in the elements.

The following are recorded highest heat indices in this three day period;

Near Hudson 110 degrees|Spring Valley 110 degrees.

What forecasters said that day

The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Twin Cities, MN wrote its last area forecast discussion before the first event at Jul 20, 12:30 PM CST, 30 minutes earlier.

Area forecast discussion, Jul 20, 12:30 PM CST, 30 minutes before

Area Forecast Discussion...UPDATED
National Weather Service Twin Cities/Chanhassen MN
130 PM CDT WED JUL 20 2016

.SHORT TERM...(Today and tonight)
Issued at 356 AM CDT Wed Jul 20 2016

Scattered showers and thunderstorms have popped in west central MN
overnight and the general expectation is for that activity to evolve
east from 09Z to 12Z this morning, with the highest pops across
south central MN.  The activity is at odds with the GFS and NAM
which likely hold back on precip development due to warmer air aloft
(700mb temps of +12C).  Many of the CAMs came in to a little bit of
agreement overnight, following the lead of the operational HRRR. The
ECMWF also hinted at precip across southern MN into western WI.
Decided to cancel the Flash Flood Watch though, as development as
been subdued and the low level jet will be weakening through the
remainder of the morning.

Expecting the precip and cloud cover to move east of I-35 by about
noon today, but could linger through a good portion of the afternoon
in western Wisconsin.  Some of the hi-res guidance wants to produce
more showers and thunderstorms this afternoon, but we are not buying
it at this time with the thinking that the mid level warming will be
too much for any vertical growth to overcome.

The previous forecast for todays highs looked really good, so just a
few minor tweaks were made to highs across the area.  Still
expecting low 90s with dewpoints well into the 70s across south
central MN, possibly approaching 80s especially for locations that
see measurable precipitation this morning.  This combination of heat
and humidity brings our heat index values in the 100 to 110 degree
range across all of southern and central MN.  In western WI, lower
temperatures due to the thermal ridge being off to the west and the
lingering cloud cover.  For this reason, continued the Excessive
Heat Watch for Thursday in the Wisconsin counties.  Today will be
hot and humid there as well, and heat indices will be in the upper
90s.

Tonight is going to be very warm and humid as advertised.  Again,
only minor tweaks needed to the overnight low forecast. The thermal
ridge aloft will really push through our area overnight tonight,
which will make tonight the warmest nighttime during this heat wave.
This is a dangerous situation for those with no air conditioning as
lows of 75 to 80 degrees and dew points around 70 to 75 will provide
little relief from the heat.

.LONG TERM...(Thursday through Tuesday)
Issued at 356 AM CDT Wed Jul 20 2016

There are two concerns in the long term. The first is the heat
wave peaking on Thursday but lingering through Friday. The second
concern is severe weather potential from Friday night through
Saturday night.

Confidence remains high across the MN CWA for the excessive heat
warning on Thursday as heat and humidity peak. Afternoon heat
indices from 105 to 112 degrees cover much of the MN CWA. The
exception is north of the Twin Cities, around Onamia, Mora and
Cambridge, where we issued a heat advisory for heat indices in
the 100 to 105 degree range. We held on the excessive heat watch
for the WI CWA for Thursday, instead of going with a warning,
primarily due to convective concerns. Some deterministic
solutions, as well as CAMS, are trying to generate convection
along the frontal boundary that slips slowly southeast across the
FA on Thursday. Although 700 mb temperatures of +14 deg C are
progged across the MN CWA on Thursday, temperatures drop off
heading east across WI with convection certainly possible. If
later model/CAM trends negate the convection, then it's a green
light for an excessive heat warning with heat indices similar to
those in the MN CWA.

The boundary that moves through on Thursday will switch the
surface flow around to the north Thursday night and early Friday.
This will result in much lower dew points (middle 60's) working
into area. An exception is along I-90 where lower to middle 70 dew
points may remain. High temperatures on Friday will still be hot,
with 90-95 degrees FA wide. However, with the lower dew points we
are failing to meet heat advisory criteria across the FA except
along the IA border. Collaboration with surrounding offices on
adjusting headlines for Friday, either to drop down to an advisory
or cancel altogether was met with a wait and see on how the
boundary situation works out. This was another reason for the
watch continuing in our WI CWA through Friday due to the
uncertainty.

Switching gears into the weekend, a more organized and rather
strong low pressure system will move through. First, the boundary
that moves through on Thursday will move back north Friday night
and early Saturday as a warm front. Convection will likely develop
in ND and slide southeast along the front late Friday night and
Saturday. This will be followed by a cold frontal passage late
Saturday into Sunday with more showers and thunderstorms
developing. There is certainly potential for severe weather and
heavy rainfall as this system moves through during the weekend.

We may salvage a dry day on Monday but then another low pressure
system will likely be right on our western doorstep by Tuesday
bringing more showers and thunderstorms to close the long term.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 130 PM CDT Wed Jul 20 2016

MVFR cigs continue to linger near AXN, but bases are beginning to
rise and clouds should scatter this afternoon. Elsewhere, VFR
conditions are expected through the period.

KMSP...No additional concerns.

/OUTLOOK FOR KMSP/
Thu...VFR. Wind SSW at 5-10kts.
Fri...VFR. Chc -TSRA late. Wind SE 5 kt.
Sat...VFR. Chc -TSRA late. Wind S-SE 5-10 kt.

&&

.MPX Watches/Warnings/Advisories...
WI...Excessive Heat Warning until 7 PM CDT Friday for WIZ024-026.

     Excessive Heat Warning from noon to 10 PM CDT Thursday for
     WIZ014>016-023-025-027-028.

MN...Excessive Heat Warning until 7 PM CDT Friday for MNZ054-056-
     060>070-073>078-082>085-091>093.

     Excessive Heat Warning until 10 PM CDT Thursday for MNZ041>045-
     047>053-055-057>059.

&&

SHORT TERM...SPD
LONG TERM...RAH
AVIATION...BORGHOFF

Hazardous weather outlook, Jul 20, 12:28 PM CST, 32 minutes before

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
128 PM CDT WED JUL 20 2016

MNZ041>045-047>070-073>078-082>085-091>093-WIZ014>016-023>028-
211830-
DOUGLAS-TODD-MORRISON-MILLE LACS-KANABEC-STEVENS-POPE-STEARNS-
BENTON-SHERBURNE-ISANTI-CHISAGO-LAC QUI PARLE-SWIFT-CHIPPEWA-
KANDIYOHI-MEEKER-WRIGHT-HENNEPIN-ANOKA-RAMSEY-WASHINGTON-
YELLOW MEDICINE-RENVILLE-MCLEOD-SIBLEY-CARVER-SCOTT-DAKOTA-
REDWOOD-BROWN-NICOLLET-LE SUEUR-RICE-GOODHUE-WATONWAN-BLUE EARTH-
WASECA-STEELE-MARTIN-FARIBAULT-FREEBORN-POLK-BARRON-RUSK-
ST. CROIX-PIERCE-DUNN-PEPIN-EAU CLAIRE-
128 PM CDT WED JUL 20 2016

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
MINNESOTA...EAST CENTRAL MINNESOTA...SOUTH CENTRAL MINNESOTA...
SOUTHEAST MINNESOTA...SOUTHWEST MINNESOTA...WEST CENTRAL
MINNESOTA...NORTHWEST WISCONSIN AND WEST CENTRAL WISCONSIN.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A HEAT WAVE WILL BEGIN TO UNFOLD TODAY WITH AFTERNOON HEAT
INDICES FROM 100 TO 110 DEGREES. THE RISK FOR HEAT ILLNESS WILL
INCREASE FOR THOSE OUTDOORS FOR PROLONGED PERIODS OF TIME.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

DANGEROUS HEAT WILL CONTINUE ON THURSDAY AND LAST INTO FRIDAY
WITH AFTERNOON HEAT INDICES FROM 100 TO 110 DEGREES.

THERE ARE CHANCES FOR A FEW THUNDERSTORMS ON THURSDAY ACROSS
CENTRAL MINNESOTA AND WEST CENTRAL WISCONSIN. THE THREAT FOR
SEVERE WEATHER IS LOW AT THIS TIME.

MORE THUNDERSTORMS ARE POSSIBLE ACROSS THE ENTIRE PLANNING AREA
FRIDAY NIGHT INTO SUNDAY. A FEW OF THESE STORMS COULD BE SEVERE
AS WELL AS CONTAIN HEAVY RAINFALL.

.SPOTTER INFORMATION STATEMENT...

SKYWARN SPOTTER ACTIVATION WILL NOT BE NEEDED.

In the hours before

Local storm report, Jul 20, 10:06 AM CST, 2 hours 54 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1106 AM CDT WED JUL 20 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1045 AM     HAIL             3 S REEVE               45.20N 92.12W
07/20/2016  M1.75 INCH       DUNN               WI   LAW ENFORCEMENT

            COUNTY SHERIFF REPORTED GOLFBALL SIZED HAIL
            IN NEW HAVEN TOWNSHIP. .

&&

MKM

Local storm report, Jul 20, 10:07 AM CST, 2 hours 53 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1107 AM CDT WED JUL 20 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1045 AM     TSTM WND DMG     3 S REEVE               45.20N 92.12W
07/20/2016                   DUNN               WI   LAW ENFORCEMENT

            COUNTY SHERIFF REPORTED TREES DOWN IN NEW
            HAVEN TOWNSHIP.

&&

MKM

Local storm report, Jul 20, 10:11 AM CST, 2 hours 49 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1111 AM CDT WED JUL 20 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1100 AM     HAIL             3 S REEVE               45.19N 92.12W
07/20/2016  M1.75 INCH       DUNN               WI   LAW ENFORCEMENT

            COUNTY SHERIFF REPORTED THAT GOLFBALL SIZED
            HAD BEEN FALLING FOR 15 MINUTES /AS OF 11
            AM/ IN NEW HAVEN TOWNSHIP. .

&&

MKM

Local storm report, Jul 20, 10:20 AM CST, 2 hours 40 minutes before

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1120 AM CDT WED JUL 20 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1005 AM     HAIL             5 SSW CUMBERLAND        45.48N 92.07W
07/20/2016  M1.25 INCH       BARRON             WI   PUBLIC

            HALF DOLLAR SIZED HAIL WAS REPORTED VIA
            FACEBOOK IN COMSTOCK. .

&&

MKM

The radar

The national radar mosaic for the moment the first event began.

Open the radar archive at this moment

Event by event

6 excessive heat. Local standard time, as filed.

Excessive Heat, St. Croix

When: July 20, 1:00 PM CST to July 21, 7:00 PM CST
Where: St. Croix forecast zone
Reported by: Mesonet
Coordinates: 45.034, -92.453 (the zone’s center; the record gives no point)

Several surface observations across St. Croix County measured heat indices over 105 degrees for several hours during the afternoon of Wednesday, July 20th, and again Thursday afternoon July 21st. Temperatures only managed to fall into the mid to upper 70s during the morning of July 21st, and rebounded into the 80s and 90s once again by the afternoon. The highest heat index was 110 degrees along the St. Croix River.

Excessive Heat, Polk

When: July 20, 1:00 PM CST to July 21, 7:00 PM CST
Where: Polk forecast zone
Reported by: Mesonet
Coordinates: 45.461, -92.441 (the zone’s center; the record gives no point)

Several surface observations across Polk County measured heat indices over 105 degrees for several hours during the afternoon of Wednesday, July 20th, and again Thursday afternoon July 21st. Temperatures only managed to fall into the mid to upper 70s during the morning of July 21st, and rebounded into the 80s and 90s once again by the afternoon. The highest heat index was 108 degrees along the St. Croix River.

Excessive Heat, Dunn

When: July 20, 1:00 PM CST to July 21, 7:00 PM CST
Where: Dunn forecast zone
Reported by: Mesonet
Coordinates: 44.947, -91.896 (the zone’s center; the record gives no point)

Several surface observations across Dunn County measured heat indices over 105 degrees for several hours during the afternoon of Wednesday, July 20th, and again Thursday afternoon July 21st. Temperatures only managed to fall into the mid to upper 70s during the morning of July 21st, and rebounded into the 80s and 90s once again by the afternoon. The highest heat index was 107 degrees.

Excessive Heat, Pierce

When: July 20, 1:00 PM CST to July 21, 7:00 PM CST
Where: Pierce forecast zone
Reported by: Mesonet
Coordinates: 44.720, -92.422 (the zone’s center; the record gives no point)

Several surface observations across Pierce County measured heat indices over 105 degrees for several hours during the afternoon of Wednesday, July 20th, and again Thursday afternoon July 21st. Temperatures only managed to fall into the mid to upper 70s during the morning of July 21st, and rebounded into the 80s and 90s once again by the afternoon. The highest heat index was 110 degrees along the Mississippi River.

Excessive Heat, Pepin

When: July 21, 1:00 PM CST to July 22, 7:00 PM CST
Where: Pepin forecast zone
Reported by: Mesonet
Coordinates: 44.483, -92.150 (the zone’s center; the record gives no point)

Several surface observations across Pepin County measured heat indices over 105 degrees for several hours during the afternoon of Thursday, July 21th, and again Friday afternoon July 22nd. Temperatures only managed to fall into the mid to upper 70s during the morning of July 22nd, and rebounded into the 80s and 90s once again by the afternoon. The highest heat index value was 110 degrees along the Mississippi River.

Excessive Heat, Eau Claire

When: July 21, 1:00 PM CST to July 22, 7:00 PM CST
Where: Eau Claire forecast zone
Reported by: Mesonet
Coordinates: 44.727, -91.286 (the zone’s center; the record gives no point)

Several surface observations across Eau Claire County measured heat indices over 105 degrees for several hours during the afternoon of Thursday, July 21th, and again Friday afternoon July 22nd. Temperatures only managed to fall into the mid to upper 70s during the morning of July 22nd, and rebounded into the 80s and 90s once again by the afternoon. The highest heat index value was 109 degrees.

What these are

Excessive Heat: Heat at or above the local excessive heat warning criteria, or heat that caused deaths.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

Every storm in Wisconsin in 2016 Every state in 2016 This day in weather history Warnings in Wisconsin, July 2016

Sources

NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 653423, 653427, 653430, 653432, 653436, 653443.