Denver’s July Weather and June Summary

June Summary

June finished up with a total of 1.62 inches of rain, which is .36 inches below normal. The average temperature was 70.8 degrees F, which is 3.4 degrees above normal. I find the precipitation number to be a bit misleading since the official Denver station is at DIA. The airport only recorded a trace of rain while downtown got pounded by a strong thunderstorm on the 28th. Finishing up the month 3.4 degrees above average is pretty significant, but not enough to get in the top 5 warmest June’s. 12 days were above 90 degrees with 98 as the hottest temperature recorded.

July Climatology

July is Denver’s hottest month on average with normal highs in the upper 80’s and low 90’s, and average low’s around 60. July tallies 2.16 inches of rain on average, almost a full inch less than June! (With .61 inches of rain already recorded on the 1st of this month, we’re already 1/4th the way there!) The typical day consists of a warm sunny morning, and hot early afternoons followed by afternoon clouds and showers, more so towards the end of the month when the North American Monsoon kicks in. The North American Monsoon is a seasonal change in the upper level patterns. The subtropical ridge, which has clockwise flow around it, is usually centered just to our east or south brining moist air all the way from the Gulf of Mexico. This is moisture in the upper levels, which usually translates to high-based thunderstorms that don’t provide a whole lot of rain, and can be wildfire starters. Cool fronts from the north can slip in cooling things off about 10 degrees and helping to spark some storms.

July 2016 Outlook

Looking at patterns that could affect our monthly weather, one major player is the ENSO oscillation (El Nino and La Nina) over the tropical Pacific Ocean. Summer effects are less so than other seasons, but there is still some correlation. In years transitioning from an El Nino to a La Nina as we likely are this year, July was slightly warmer and wetter than average (Figures 1, 2). The average upper level pattern during those years had a ridge centered just to our south, bringing the usual monsoonal moisture our way (Figure 3). There are other oscillations that can alter long-term weather patterns such as the Pacific North American Oscillation, but those patterns don’t have a whole lot of correlation to our weather in July. Current CFS model runs show a general trough to our west and in our area during the second week of the month indicating normal to slightly cooler temperatures. The subtropical high is shown to build back in during the second half of the month leading to warm temperatures and some monsoonal flow. The Climate Prediction Center is calling for a slightly warm and dry first half of the month, and a warm second half with near average precip.

Enjoy the weather!


(Figure 1) Temperature Anomalies in Celsius, warm colors are above average temperatures, cool colors below normal.


(Figure 2) Precipitation anomalies in mm per day. Blue colors indicate above average precip.


(Figure 3) Average 500mb Heights with clockwise flow around the High pressure center

Chance of Thunderstorms, then Heat!

Thunderstorms are expected to develop in the evening hours on Monday, with a better chance of rain on the South and West sides of town. There is also a chance of storms in the afternoons on Tuesday and Wednesday. Some storms could be strong with high winds and decent sized hail on Tuesday if they are able to get going. Temperatures should be in the low to mid 80’s for highs each day. The weather will turn hot with temperatures around 90 from Thursday through the weekend. An approaching system may cool us down a bit next Monday. There will be a small chance for storms each day, mainly in the mountains and on the Palmer Divide.

Enjoy the weather and don’t forget the sunscreen!

Denver’s June Weather

June is typically warm and pleasant in the Denver area, with average highs ranging from the upper 70’s at the start of the month to the mid 80’s at the end of the month. Rainfall usually comes in the form of thunderstorms, some of which can be severe as June is part of Denver’s severe weather season. Cold fronts coming from the north bring cooler temperatures, but can also enhance the severe weather threat a day or two later, as moisture sometimes is pushed into the area from easterly winds. June can also feature very hot temperatures, as was the case in 2012 when Denver tied its all-time record high of 105º F, two days in a row on the 25th and 26th in a 5 day heat wave featuring highs above 100 every day.

The intense El Nino event that occurred over the last year has weakened rapidly and will likely transition to a La Nina in the fall and winter. The ENSO cycle as it’s called, can lead to changes in the upper level weather patterns across the globe, including the US. Comparing four previous years with a transition from El Nino to La Nina conditions in the summer (1988, 1998, 2007, 2010). Warmer than normal temperatures occurred in the center of the country, with Denver averaging about 1.4º F warmer than average on those years (Figures 1 and 2). Rainfall was also less than normal during these transition years, averaging about 0.7 inches less (Figure 3). Denver’s average June rainfall is just under 2 inches, which translates to about a third less rainfall than normal during the transition years.


Figure 1 Average Air Temperature for June in Celsius. (16C = 61F)


Figure 2 Difference from Average Temperature During Transition Years (Warm colors are hotter, cool colors are colder)


Figure 3 Difference from Average Rainfall During Transition Years (Warm colors show less rain, cool colors are more)

2016 Outlook

(A brief explanation of what upper level ridges and troughs mean: Ridges are usually associated with dry and warm weather, while troughs are associated with cooler and more unsettled weather.)

Looking ahead to this June, weather models show a ridge in the jetstream to the west and near our area for about the first 10 days, indicating generally dry and warm conditions (Figure 4). That could change around the 8th, when we could see a weather system bring us a few thunderstorms and cooler temperatures. A stronger system is predicted to move into our area around the 10th, bringing cooler temperatures and the chance for more precipitation. Beyond this, the GFS (a mid range weather model) has a general ridge centered over us or just to our west mid-month, while the CFS (a long range climate model) has a ridge centered to our east. Both models have warm temperatures either way.


Figure 4 Jetstream on June 5th

Looking farther out gets tricky, as models rarely make the correct forecast. However, the CFS does a pretty good job at predicting general trends, and it has been showing an upper level ridge centered to our east and a trough to our west for most of the remainder of June. If this verifies, we could see generally warmer conditions to finish the month. (Sounds a lot like the pattern in the previous transition years doesn’t it?)

The Climate Prediction Center is calling for a warmer first half of June, with about average precip. The rest of the month is shown to have equal chances of above or below temperatures and precipitation. Only time will tell!


Enjoy the weather! I will likely be posting monthly outlooks and other interesting events in the future.



For more info about these topics check out:

(El Nino Discussion)

(Climate Re-analyzer)