An unusually strong ridge of high pressure settled over the Pacific Northwest bringing hot daytime temperatures and warm overnight lows. The consecutive days of heat made it difficult to cool locations without air conditioning.
Every event with a place to put it; 4 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
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 MSO wrote it up.
An unusually strong ridge of high pressure settled over the Pacific Northwest bringing hot daytime temperatures and warm overnight lows. The consecutive days of heat made it difficult to cool locations without air conditioning. Daily record highs were set for several observation sites.
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 Jun 27, 12:51 PM PST, 2 hours 9 minutes earlier.
Area Forecast Discussion
National Weather Service Missoula MT
251 PM MDT Sun Jun 27 2021
...DANGEROUS HEAT ACROSS NORTHERN ROCKIES THROUGH COMING WEEK...
.DISCUSSION...
Dangerously hot daytime and overnight temperatures are expected for
much of the Northern Rockies throughout the coming week. High
pressure centered over the coastal Pacific Northwest will slowly
drift eastward through the middle of the coming week, increasing
temperatures toward record warmth. Ambient conditions will be almost
exclusively dry, however there is a very low chance of a stray
terrain-based thunderstorm briefly developing Monday and/or Tuesday.
We cannot stress enough what kind of toll the impending heat will
have on individuals spending time outside throughout the next week.
Despite cooling overnight and thunderstorm chances increasing after
Wednesday, the long-lasting and exceptional warmth (both day and
night) can have compounding negative health effects for both people
and animals. Make a plan to seek out relief from the heat regularly
and drink plenty of water. If you remember the heatwave that was
July 2007, then you will know what kind of pattern the Northern
Rockies will be stuck in for a least this coming week.
Showers and thunderstorms will be begin to characterize each
afternoon and evening across the Northern Rockies Thursday through
next weekend. The focus of convection will be primarily north
central Idaho, southwest Montana, and along the Continental Divide.
The resulting clouds will slightly cool daytime temperatures, while
simultaneous warming overnight temperatures.
There are signs that a bit of a cooler pattern and increased
thunderstorm activity will develop across the Northern Rockies in
the 7-10 day forecast period, however there is still little clarity
about the impact of this change (e.g., if strong thunderstorms will
develop during the transition).
&&
.AVIATION...Northeast winds aloft will be accompanied by fair
weather cumulus over the Northern Rockies during the next 24
hours. Surface winds will gust to 25 knots at times through
28/0300Z. Northeast winds cloud cover will mostly dissipate within
area valleys thereafter, however ridgetop winds will remain
east/northeast through Monday.
&&
.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Heat Advisory from noon Tuesday to 8 PM MDT Thursday
Bitterroot/Sapphire Mountains...Missoula/Bitterroot
Valleys...Potomac/Seeley Lake Region.
Excessive Heat Warning from noon Monday to 8 PM MDT Thursday
Kootenai/Cabinet Region...Lower Clark Fork Region.
Heat Advisory from noon Tuesday to 8 PM MDT Thursday
Flathead/Mission Valleys...West Glacier Region.
ID...Heat Advisory from noon Tuesday to 8 PM MDT Thursday Eastern
Lemhi County...Western Lemhi County.
Excessive Heat Warning until 7 PM PDT Thursday Northern
Clearwater Mountains...Southern Clearwater Mountains.
Excessive Heat Warning until 7 PM PDT Thursday Lower Hells
Canyon/Salmon River Region...Orofino/Grangeville Region.
&&The national radar mosaic for the moment the first event began.
4 heat. Local standard time, as filed.
Highs temperatures reached from 100 to 110 degrees Fahrenheit with overnight lows in the upper 60s to lower 70s. Orofino peaked out at 112 degrees on the 29th.
Overnight lows only dropped into the 60s after daytime highs reached 100 to 110 degrees at the lower elevations.
High temperatures ranged from the upper 90s to 107 degrees at lower elevations with overnight lows in the 60s.
High temperatures ranged from 100 to 110 degrees with overnight lows generally in the 60s. There were some exceptions, such as the observation site at Pittsburg Landing reaching 115 degrees on the 29th with a morning low that day of 78 degrees.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2021Every state in 2021This day in weather historyWarnings in Idaho, June 2021
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: 959422, 959423, 959424, 959425.