Idaho, 2018Excessive Heat in Idaho, August 9 to 10, 2018
August 9 to 10, 2018 · NWS MSO · 3 events in 3 counties and zones
A ridge of high pressure brought a record breaking heat wave across lower elevations in north central Idaho August 9th and 10th.
Every event with a place to put it; 3 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
- Tornadoes
- Tropical storms and surge
- Floods
- Wind
- Hail
- Winter weather
- Heat and drought
- Cold
- Fire, smoke and dust
- Marine and coastal
- Other
Open the live radar over this ground
- Deaths
- 0
- Injuries
- 0
- Property damage
- None recorded
- Crop damage
- None recorded
- Events
- 3
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.
A ridge of high pressure brought a record breaking heat wave across lower elevations in north central Idaho August 9th and 10th.
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 Missoula, MT wrote its last area forecast discussion before the first event at Aug 9, 1:26 AM PST, 9 hours 34 minutes earlier.
Area forecast discussion, Aug 9, 1:26 AM PST, 9 hours 34 minutes before
Area Forecast Discussion
National Weather Service Missoula MT
326 AM MDT Thu Aug 9 2018
...Near Record Heat Today and Friday...
.DISCUSSION...Temperatures today and Friday will be the warmest we
have seen all year across the Northern Rockies. The ridge of high
pressure will continue to build and strengthen over the region
through Friday. The trough of low pressure that was expected to
move through the Northern Rockies Friday, has slowed, and now
looks to move though Saturday afternoon and evening. This will
translate into Friday being the warmest day of the week. Areas
around Orofino, Fenn, and Pierce, Idaho could be flirting with
their all-time record high for August. Due to the expected heat,
the Heat Advisory has been upgraded to an Excessive Heat Warning
in these areas, through Friday. Heat exhaustion will likely occur
during strenuous outdoor activities in this type of hot weather.
A Heat Advisory remains in place for portions of western Montana,
where some locations are expected to reach 100+ degrees.
As mentioned above, a primarily dry cold front will move through
the region during the day on Saturday. This will bring gusty
southwesterly winds up to 30 mph or higher at times Saturday
afternoon and evening. There could be isolated rain showers
and/or thunderstorms across northwestern Montana, but not
expecting a lot of rain out of what does develop. Temperatures
will drop back down to normal for this time of year.
Temperatures will be noticeably cooler for Sunday, though some
leftover breezy winds are likely through the Sunday and Sunday
night period. Much calmer conditions and near normal temperatures
will return for early next week. There is a potential for isolated
showers and thunderstorms to develop during the mid-week over
southwest Montana and Lemhi County, but details on timing are
still uncertain at this time.
&&
.AVIATION...VFR conditions under clear skies are expected in the
next 24 hours, though increased smoke/haze could reduce visibility.
This reduced visibility is most likely over northwest Montana,
and central Idaho. Density altitudes will increase during peak
heating hours.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Fire Weather Watch from Friday afternoon through Saturday
evening Bitterroot...Deerlodge/West Beaverhead...East
Beaverhead...East Lolo...Flathead/Glacier Park...Salish and
Kootenai Reservation.
Heat Advisory from 3 PM this afternoon to 9 PM MDT Friday
Flathead/Mission Valleys...Kootenai/Cabinet Region...Lower
Clark Fork Region...Missoula/Bitterroot Valleys...
Potomac/Seeley Lake Region...West Glacier Region.
Fire Weather Watch from Friday afternoon through Saturday
evening Kootenai...West Lolo.
ID...Excessive Heat Warning until 8 PM PDT Friday Lower Hells
Canyon/Salmon River Region...Northern Clearwater
Mountains...Orofino/Grangeville Region.
Fire Weather Watch from Friday morning through Saturday evening
Clearwater/Nez Perce...Palouse/Hells Canyon.
&&Excessive Heat, Northern Clearwater Mountains
- When
- August 9, 11:00 AM PST to August 10, 7:00 PM PST
- Where
- Northern Clearwater Mountains forecast zone
- Reported by
- COOP Observer
- Coordinates
- 46.674, -115.657 (the zone’s center; the record gives no point)
Pierce set a record high of 101 on August 9th and an all-time record high of 105 on August 10th. The two day mean maximum temperature of 103 at Pierce was the hottest on record with observations going back to 1963. Elk River reached a high of 98 on the 9th and then set a record high of 102 on August 10th. Even though RAWS sites have displayed a warm bias, the Dent RAWS in close proximity to the Dworswak Reservoir reached 106 on the 9th and 105 on August 10th.
Excessive Heat, Orofino / Grangeville Region
- When
- August 9, 11:00 AM PST to August 10, 7:00 PM PST
- Where
- Orofino / Grangeville Region forecast zone
- Reported by
- COOP Observer
- Coordinates
- 46.259, -115.562 (the zone’s center; the record gives no point)
Cottonwood set record highs of 103 on the 10th and 99 on the 9th. The two day mean maximum temperature of 102 is the hottest two day stretch since observations began in 1976. Grangeville reached 104 on the 10th and 99 on the 9th. Kamiah just inside Spokane's County Warning Area recorded the second hottest two day mean maximum temperature stretch with 109.5. Kamiah set record highs of 109 on the 9th and 110 on the 10th.
Excessive Heat, Lower Hells Canyon / Salmon River Region
- When
- August 9, 11:00 AM PST to August 10, 7:00 PM PST
- Where
- Lower Hells Canyon / Salmon River Region forecast zone
- Reported by
- Mesonet
- Coordinates
- 45.844, -115.467 (the zone’s center; the record gives no point)
The Pittsburg RAWS reached 116 on the 9th and 119 on the 10th. RAWS have a well documented warm bias, so these temperatures are difficult to compare to other observations. Nevertheless, in this notoriously hot location, 119 appears to be the warmest in its period of record going back to 1993. Furthermore, the Slate Creek RAWS reached 113 on the 9th and 114 on the 10th. Finally, Riggins reached 109 on the 10th, one degree shy of the record high of 110, with observations going back to 1896.
- 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.
- Damaging Winds and Lightning Strike in Texas, August 9 to 11, 2018$400,000 · 50 kt wind · 4 events
- Flash Flooding and Dust Storm in Arizona, August 9 to 11, 20182 injured · $132,000 · 54 kt wind · 9 events
- Tornado and Flash Flood in New Mexico, August 9, 2018$300,000 · EF0 · 7 events
- Dust Storm and Hail in Nevada, August 9 to 11, 2018$170,000 · 1 in hail · 8 events
- Flooding and Damaging Winds in Massachusetts, August 9, 2018$58,000 · 50 kt wind · 10 events
- Damaging Winds and Heavy Rain in Arizona, August 9, 2018$48,000 · 61 kt wind · 6 events
- Damaging Winds and Lightning Strike in South Carolina, August 9, 20181 injured · $3,000 · 55 kt wind · 30 events
- Tornado and Hail in Wisconsin, August 9, 2018$51,000 · EF0 · 3 events
- Damaging Wind in Arizona, August 9, 2018$30,000 · 61 kt wind · 1 event
- Damaging Winds in New York, August 9, 2018$19,000 · 61 kt wind · 2 events
- Flash Flooding and Heavy Rain in Arizona, August 9 to 10, 2018$15,000 · 4 events
- Marine Thunderstorm Winds in South Atlantic Coastal Waters, August 9, 201850 kt wind · 8 events
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: 770823, 770827, 770832.