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7th Day of 100+F Heat In Denver, CO; June 2012 Hottest On Record For CO

It’s official: June 2012 was the hottest June on record in Denver, CO (dating back to 1872) with an average temperature of 75F, 7.6F above normal!

Yesterday’s high of 101F added to the total number of days of 100F+ temperatures: to date, there are now 7. Last week, there were 5 days in a row of 100F+ heat, matching the all-time record for Denver. The streak included 2 105F readings, which tied for the all-time hottest temperature recorded for Denver. There was also a 100F+ reading a few days prior to that streak. For completeness, I want to point out that the 27th through 30th of June weren’t much cooler: it was 97, 97, 98, and 99 on those four days, so we didn’t miss 100 by much.

Here are a few pictures demonstrating the intensity and extent of the heat that affected not only Denver, but much of the High Plains prior to the impacts east of the Mississippi over the weekend:

Figure 1. Contour plot of surface maximum temperatures for July 1, 2012. [more graphs and records below the fold]

Figure 2. Plot of surface maximum temperatures by station for July 1, 2012.

Figure 3. Contour plot of surface maximum temperatures for June 30, 2012.

Figure 4. Contour plot of surface maximum temperatures for June 29, 2012.

Figure 5. Plot of surface maximum temperatures by station for June 26, 2012. This is one of the two dates that Denver’s temperature tied for the all-time recorded high of 105F.


Last year, there were 50 consecutive days of 90F+ maximum temperatures at Denver, which tied for 9th-longest in our recorded history. With 7 additional days, it would have been the 3rd-longest streak; 11 more days would have tied the longest streak on record, set in 2000. Note also that 6 of the 11 longest streaks have occurred in the 21st century! Normally, Denver experiences ~34 days of 90F+ maximum temperatures.

So far this year, we are in the middle of a 10-day streak. Today, the temperature has already been over 90 for over 4 hours (now 2:30P local) and the forecast calls for 90F+ for at least the next 5 days.

I couldn’t find records on the average number of 100F days in Denver in a year. I would venture a guess and say that is because the number is less than one. I’ll do some more digging and see if I can find out one way or the other.

Climate Projections

It wasn’t that long ago that I first saw projections of potential future climate maps for the US and didn’t think I could imagine what it would be to live through such conditions. I’m sure there are many people who either similarly couldn’t imagine it because it hasn’t happened yet or who are simply unaware of such projections. Take a look at the following graphic:

Figure 6. Projection for 2090-2099 of the number of weeks per year where maximum daily temperatures exceed 100F. This projection used the A1FI SRES scenario, which best represents the globe’s current emissions path.

For the sake of conversation, I will assume that Denver has so far this year experienced 1 week (7 days) of 100F+ temperatures, and will further assume that no additional 100F days will occur in the rest of the year. Under the A1FI scenario, by the end of this century, such a year would be considered relatively cool!

This shift toward more extreme temperatures can also be represented in this graphical manner:

This graphic shows that the increase in average temperature does not have to be that large in magnitude in order for a sizable number of events at the tail of a distribution (e.g., temperature) to occur.

Millions of people are currently without power (due to violent thunderstorms) and are experiencing 100F+ temperatures in the eastern US. How many more summers like this do they want to have? They’re going to find out, that’s very nearly certain now.

Cross-posted at WeatherDem – the blog.

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John has been writing for Firedoglake since 2006 or so, on whatever interests him. He has a law degree, worked as legal counsel and energy policy adviser for a state energy agency for 20 years and then as a consultant on electricity systems and markets. He's now retired, living in Massachusetts.

You can follow John on twitter: @JohnChandley