BOISE, Idaho — If you've stepped outside at any point throughout the day in the last 72 hours, you've probably noticed the extreme heat ravaging the Treasure Valley.
Monday marks the first day of a six or seven-day stretch of 100-degree weather, with mid-week temperatures capping out at nearly 106 degrees.
Triple-digit temperatures have always been the touchstone for summer temperatures. While June 2021 is shaping up to be a warm one, Idaho has already had one 100-degree day and temperatures are already seven degrees warmer than average.
How does this stretch of heat stack up to the recorded history of Boise summers?
Situated in a high desert, it's not unusual that summers in the City of Trees are typically very hot. Between 1940 and 1990, however, Boise only reached 100 degrees an average of five days a season, according to the National Weather Service.
In those 50 years, there were four recorded instances in which temperatures reached triple digits at least 10 times.
However, the frequency of these high temperatures began to increase in 1990. Since then, Boise has experienced 14 years of ten or more 100 degree days. 11 of those years have been since 2000.
Since 2003, Boise has averaged nearly 11 days above 100 degrees per year, which has raised the overall average from five days to six days. The five-day average was set in 1940.
Beginning on July 15, 2003, nine consecutive days of triple-digit temperatures were recorded. The previous record was set in 1960 with seven consecutive days of triple-digit temperatures.
Those nine days in 2003 were just the beginning. By the end of the summer, Boise recorded 20 days of triple-digit temperatures.
Three years later, there were nine more days of consecutive triple-digit temperatures. The 2006 summer ended with 16 total days of record-high temperatures.
Another nine-day stretch of triple-digit temperatures was recorded in 2015. On June 28, 2015, the temperature reached 110 degrees, just one degree shy of a record.
The city of Boise has been recording temperatures at the Boise Airport since 1940. Prior to this, temperatures were recorded at various spots around town.
In those history books, 1865 was the only recorded year hotter than 2015.
Boise has hit 110 degrees five times since 1960, and four of those times have been in the last 20 years.
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