Late day and evening thunderstorms becoming strong in portions of central Wyoming. To the southwest of Cody, nickel sized hail was reported.
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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.
The episode as NWS RIW wrote it up.
Late day and evening thunderstorms becoming strong in portions of central Wyoming. To the southwest of Cody, nickel sized hail was reported. In Riverton, a strong thunderstorms produced large amounts of hail up to penny size that accumulated a few inches in some locations. Very heavy rain accompanied the hail, with a retired National Weather Service meteorologist reporting 1.40 inches of rain and melted hail in only 30 minutes. As a result, there were numerous reports of minor street flooding and some flooded basements.
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 Riverton, WY wrote its last area forecast discussion before the first event at Jun 24, 5:00 PM MST, 2 hours 25 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Riverton WY 600 PM MDT Wed Jun 24 2026 .KEY MESSAGES... - Scattered showers and thunderstorms become more widespread through Wednesday evening and overnight as a weather system moves into the state from Utah. These showers and storms continue to move east through the forecast area Thursday morning. - Gusty outflow wind 40 to 50 mph, brief heavy rain, and small hail will be the primary hazards associated with Wednesday night and Thursday morning showers and thunderstorms. - Another round of showers and thunderstorms crosses the region Thursday afternoon with gusty wind and small hail the main hazards. - A weather system moves into the Pacific Northwest Friday and heads toward Wyoming over the weekend. This leads to gusty southwest wind Friday, which elevates fire weather conditions, followed by cooler temperatures, precipitation chances, and possibly some high elevation mountain snow over the weekend. && .UPDATE... Issued at 1152 AM MDT Wed Jun 24 2026 A few adjustments with the daytime forecast update. Firstly, strong to severe thunderstorms remain possible this afternoon and evening. The Storm Prediction Center has nudged an area of marginal and slight risks further into central WY. The latest convective outlook now includes Riverton, Thermopolis, and Worland with the main hazard being large hail. Southwestern WY has also seen an adjustment in the marginal risk. Rock Springs has now been included with the main concern being dry thunderstorms which could produce strong gusty winds in excess of 55 mph. Otherwise, not much of the forecast has changed. Similar to the previous discussion the area with the greatest chances of seeing a strong to severe storm remains east of the Divide. CAMs have highlighted an area from the southern Bighorn Basin to the Wind River Basin and into Natrona County. As mentioned in the previous discussion the timing for the strongest storm development looks to be in the mid afternoon. The second round of showers and thunderstorms pushes across central and southern WY after 6 MDT. There remains a chance for an isolated strong to severe storm with this second push but chances will quickly decrease after sunset. Thursday continues to look like another active day with widespread showers and thunderstorms. Similar to the previous discussion, morning cloud cover will be the main caveat. Currently, it is looking like there should be some clearing during the mid to late morning especially across central and eastern WY. This window is quite limited with likely only a few hours of scattered to broken cloud cover. However, this may be enough to aid in fueling storms as they begin developing by the late morning and early afternoon. The main hazards with any of these storms will be strong gusty winds, frequent lightning and large hail. Friday is looking active as well with another round of showers and thunderstorms possible during the afternoon and evening. A few strong to severe storms cannot be ruled out Friday afternoon and evening. For the weekend and past, the previous discussion remains on track with not much additional information to add. && .DISCUSSION... Issued at 212 AM MDT Wed Jun 24 2026 Things are still shaping up to be rather active across the area over the next several days. And in true Wyoming fashion, we may pass through a few seasons over the next few days. The main concern today will be thunderstorms as a shortwave moves across the area, and some of them have the potential to be severe. There will be some storms around in the afternoon, but a bulk of the activity may end up being in the evening and even overnight hours. The risk of stronger storms would likely be before sunset though, when instability will be the greatest. Our partners at the Storm Prediction Center have largely kept the Marginal Risk status quo, running largely east of the Worland to Hiland line, and covering Johnson, Natrona and eastern Washakie Counties. The area of most concern is Natrona County, where a slight risk is in effect. This makes sense given CAPE is maximized here (as high as 1500 J/Kg) as well as lifted indices (as low as minus 4). The strongest storms at this point should remain East of the the area over Eastern Wyoming, but it is a bit too close for comfort. And there is another area of concern, this one across southwestern Wyoming, although the main and probably only threat here would be strong wind gusts. We will now discuss the individual threats with the storms: large hail, strong wind, tornadoes and heavy rain. Large Hail...The main threat of this looks to be in our eastern counties, mainly Johnson and Natrona Counties. This chance maximizes in southern Johnson and Natrona Counties though. Conditions are good for this as model Skew Ts show as much as 50 knots of 0 to 6 kilometer shear with large lapse rates of almost 9C / Km. There will be a cap on the atmosphere initially though, so this looks like a later show, with most worst possibly in the evening. This area also has a Conditional Instability Group Level 1, meaning hail up to golf ball size or higher. However, there is Conditional Instability Group 2 just to the east of the Casper, which means the chance of baseball sized hail. Chances of large hail do drop further west, but almost any storm to the East of the Divide could have small hail. The greatest threat of this should end around midnight as the we lose the heating of the day and instability. Strong Wind Gusts...As usual, this will be a threat with just about any shower or thunderstorm, this is Wyoming after all. There are two main areas of concern. The first is in the area similar to the large hail threat, and this area has the most instability. There is another area of concern though. And this is across southwestern Wyoming. This is more of a little green blob scenario as the shortwave approaches this evening, with soundings showing very well defined inverted V soundings resulting in some high based showers and thunderstorms. Lapse rates are very steep (as much as 9C/km) with dew point depressions over 50 degrees in some locations. The result will likely be some wind gusts over 55 mph at times in any thunderstorm, shower or even cumulus cloud when it collapses. The main threat of this will be in the afternoon and evening, then decreasing later in the evening as the atmosphere cools. Tornadoes...This again is by far the least threat, but it is not zero. There are things going for it, mainly the deep directional and speed shear. In addition, cloud bases will be lowering into the evening as the moisture increases. The main factor against it is that with slow 700 millibar flow, there may be more storm interactions and not as many stand alone supercells. The best chance of this would be in eastern Natrona County, but even here the chance is only 2 percent, with chances decreasing further west. Heavy Rain...Most storms, but especially the ones East of the Divide will have the potential of this. Precipitable water values rise two over an inch in some locations Wednesday evening, and this gets my attention as this is 200 percent of our climatological value. Dew points will also get fairly high for these parts, rising into the 50s in our eastern counties. Flow will also be easterly up to around 700 millibars, bringing in additional moisture. One mitigating factor is that there will be decent flow at 500 millibars, anywhere from 20 to 30 knots, so the storms should have some movement. It is also been very dry across most of the area, so there is room in the soil to soak up some moisture. There will still be the chance for some localized flooding, but it should not be widespread. The best chance would be East of the Divide, where upslope flow and the greatest moisture will be found. More strong storms will be possible on Thursday. However, there will be more uncertainty here. Another shortwave will be moving across the area. The limiting factor may be cloud cover and showers that will linger across the area during the morning hours. This may limit surface heating and instability somewhat and decrease the chance of stronger storms. There will still be a decent amount of shear present though. So, if there can be some clearing, we could see another round of strong to severe storms. This will again be in areas similar to today, largely East of a Greybull to Worland to Hiland line. But the chance of stronger storms looks less than today at this time. Looking further out, Friday should be a lull with shortwave ridging over the area and less storms. Attention then turns to an upper level low that will be moving onshore in the Pacific Northwest Friday night and moving into the northern Rockies this weekend. Recent model trends have weakened the system a bit and also shifted to low a bit further to the west. This has decreased the QPF across the area. The system has also trended a bit warmer, so potential snowfall amounts in the west look less. The 700 millibar temperatures now look to bottom out around minus 1 or so, which would put snow levels around 8000 feet later Saturday night and Sunday. Nevertheless, locations above 9000 feet will likely see a light accumulation of snow during this time. This includes anyone going over Togwotee Pass as well, although most snow would melt on roads. So, the active weather pattern will continue across western and central Wyoming for the next several days. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 524 PM MDT Wed Jun 24 2026 Showers and thunderstorms will continue to increase in coverage across Wyoming, and potentially impact all terminals through the evening and overnight. Storm coverage is expected to increase from southwest to east/northeast, so the first terminal to potentially see showers or thunderstorms is KRKS followed by all other terminals. PROB30s have been maintained where confidence in timing and/or direct impacts is more uncertain. Strong to severe thunderstorms - mainly due to outflow wind gusts - are possible, mainly prior to 06Z at KCPR, KRKS, KRIW, KLND, and KWRL, with frequent lightning, gusty 50kt winds, and hail being the main hazards. Another round of showers and thunderstorms is forecast again on Thursday at most terminals. KJAC is expected to see showers or thunderstorms first around 14Z. Showers and thunderstorms then increase in coverage through Thursday morning and early afternoon. Any thunderstorms on Thursday could have gusty 40kts to 50kt winds and small hail. Outside of shower and thunderstorm activity, most terminals will remain VFR this TAF period. KCPR is the exception terminal, where MVFR clouds are forecast with prevailing light rain followed by MVFR ceilings persist through 16Z/Thursday. Breezy winds between 10kts and 15kts are expected through 03Z/Thursday. KRKS, KRIW, KPNA, and KBPI are forecast to have frequent 20kt to 30kt wind gusts the remainder of Wednesday evening. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES... None. && UPDATE...Dziewaltowski DISCUSSION...Hattings AVIATION...CNJ/Gerhardt
Special Weather Statement
National Weather Service Riverton WY
659 PM MDT Wed Jun 24 2026
WYZ019-030-250130-
East Sweetwater County-Green Mountains and Rattlesnake Range-
659 PM MDT Wed Jun 24 2026
...A STRONG THUNDERSTORM WILL IMPACT SOUTHERN FREMONT AND NORTHERN
SWEETWATER COUNTIES THROUGH 730 PM MDT...
At 659 PM MDT, Doppler radar was tracking a strong thunderstorm
capable of producing a landspout 15 miles southwest of Crooks Gap,
which is 22 miles southwest of Jeffrey City, moving northeast at 20
mph.
HAZARD...Landspouts and wind gusts up to 50 mph.
SOURCE...Radar indicated.
IMPACT...Minor damage to outdoor objects is possible. Gusty winds
could knock down tree limbs and blow around unsecured
objects.
This storm will remain over mainly rural areas of southern Fremont
and northern Sweetwater Counties.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4208 10809 4216 10826 4247 10816 4226 10766
TIME...MOT...LOC 0059Z 229DEG 18KT 4222 10807
LANDSPOUT...POSSIBLE
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...50 MPH
RoweSpecial Weather Statement
National Weather Service Riverton WY
717 PM MDT Wed Jun 24 2026
WYZ019-250145-
Green Mountains and Rattlesnake Range-
717 PM MDT Wed Jun 24 2026
...STRONG THUNDERSTORMS WILL IMPACT SOUTHEASTERN FREMONT COUNTY
THROUGH 745 PM MDT...
At 716 PM MDT, Doppler radar was tracking a cluster of strong
thunderstorms capable of producing a landspout 7 miles west of Crooks
Gap, which is 14 miles southwest of Jeffrey City, moving northeast at
20 mph.
HAZARD...Landspouts, wind gusts up to 50 mph, and penny size hail.
SOURCE...Radar indicated.
IMPACT...Minor damage to outdoor objects is possible. Gusty winds
could blow around dust.
This strong thunderstorm will be near...
Crooks Gap around 730 PM MDT.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4223 10779 4234 10816 4261 10816 4245 10753
4243 10752 4225 10752
TIME...MOT...LOC 0116Z 220DEG 17KT 4233 10799
LANDSPOUT...POSSIBLE
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH
RoweSpecial Weather Statement
National Weather Service Riverton WY
735 PM MDT Wed Jun 24 2026
WYZ018-019-250200-
Green Mountains and Rattlesnake Range-Lander Foothills-
735 PM MDT Wed Jun 24 2026
...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN FREMONT COUNTY
THROUGH 800 PM MDT...
At 734 PM MDT, Doppler radar was tracking a strong thunderstorm
capable of producing a landspout near Sweetwater Station, which is 18
miles northwest of Jeffrey City, moving northeast at 15 mph.
HAZARD...Landspouts, wind gusts up to 50 mph, and penny size hail.
SOURCE...Radar indicated.
IMPACT...Minor damage to outdoor objects is possible. Gusty winds
could knock down tree limbs and blow around unsecured
objects.
This storm will remain over mainly rural areas of southeastern
Fremont County.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4249 10811 4253 10829 4273 10845 4272 10834
4269 10831 4267 10830 4265 10828 4267 10825
4268 10821 4269 10820 4271 10820 4269 10787
TIME...MOT...LOC 0134Z 211DEG 11KT 4260 10817
LANDSPOUT...POSSIBLE
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH
RoweSpecial Weather Statement
National Weather Service Riverton WY
738 PM MDT Wed Jun 24 2026
WYZ002-250215-
Absaroka Mountains-
738 PM MDT Wed Jun 24 2026
...A STRONG THUNDERSTORM WILL IMPACT CENTRAL PARK COUNTY THROUGH 815
PM MDT...
At 738 PM MDT, Doppler radar was tracking a strong thunderstorm 8
miles east of Pahaska, which is 11 miles east of East Entrance,
moving east at 30 mph.
HAZARD...Wind gusts of 50 to 55 mph and penny size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
This storm will remain over mainly rural areas of central Park
County, including the following locations... Wapiti Campground.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4461 10945 4448 10948 4448 10950 4449 10951
4449 10953 4444 10953 4444 10949 4434 10952
4446 10991 4458 10988
TIME...MOT...LOC 0138Z 272DEG 27KT 4452 10978
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...55 MPH
RoweThe Billings radar (KBLX), 162 km away, was scanning. The volume nearest the first event began at 02:22 UTC.
2 hail. Local standard time, as filed.
A trained spotter reported nickel size hail to the southwest of Cody.
A strong thunderstorm with hail up to penny size and very heavy rain passed over Riverton, bringing accumulating hail and very heavy rain. There was a large contrast across the city, with only 0.15 inches of rain on the west end, and 1.40 inches on the east side of town. The combination of hail and very heavy rain led to minor street flooding as well as some flooded basements. The large amount of hail also damaged peoples gardens.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Wyoming in 2026Every state in 2026This day in weather historyWarnings in Wyoming, June 2026
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: 1351617, 1351618.