Return to Year 2015

July – Sept

A statistical look and discussion of weather recorded for Castle Rock Colorado. This information was collected and recorded via my weather station in the Meadows in the town of Castle Rock. It is in no way an “official” record, just simply what was recorded by my station.

July, 2015



July 2015 Drier and Warmer but Overall Typical

July 2015 was slightly warmer and slightly drier than normal but not unusually so. We would probably call this a typical July in Colorado as we saw no huge extremes either warm, cold, wet or dry.

The high temperature for July 2015 averaged out at 86.71 which makes the overall temperature about 1.51 over the average. This is was only slightly above average so not a big point of interest. Rainfall was also slightly below but very close to average. The main difference this month is that we did not get any super-soaking storms to give us larger amounts of rain. Several storms brought smaller amounts of rain to the area and the monsoon really didn’t kick in at all for July.

August, 2015


August 2015 Much Warmer than Average and Slightly Drier

August 2015 experienced much warmer than average temperatures along the front range of Colorado and Castle Rock was no exception. A stubborn ridge of high pressure over the Western United States kept the storm track mostly away from Colorado and ferried in warm air from the desert Southwest. While the plains and front range saw a glimpse of monsoon-like conditions on a couple of days, overall the August monsoon was unimpressive with a below average tally for precipitation.

The high temperature for August 2015 averaged out at 81.15 which makes the temperature for the month a respectable 4.45 degrees over the long term average.  Rainfall was also below average this month as the monsoon was never able to establish over the Rocky Mountain region.

September 2015 Sneak Preview

The climate prediction center has predicted a greater chance of a September that features below average temperatures and above average precipitation. This is in line with what we would expect with a strong El Nino pattern into Fall in Colorado.

The possibility of a monsoon setup still exists into September and with such would include a higher chance of storms and with the added cloud cover, an increased chance that temperatures to be below normal. I have considerable concern about the monsoon making a showing at all at this point. Strong ridging has been quite persistent and if that continues into September we will most likely see at least above average temperatures overall. The precipitation is a bit murkier as September is historically a very dry month. Even a couple of slightly rainy days can push it over edge.

Watch for the first week or two to showcase our abnormally warm and dry weather from August as the ridge will still be in place. Many longer range models feature the ridge breaking down the second week or so of September, allowing some cooler and wetter fall weather to establish, but should that ridge persist over the West, I don’t think I can agree with the CPC on this outlook. Stay tuned, it should make for an interesting month!

September, 2015



September 2015 Record Warmest in History and Very Dry


Clarification: This is the average high temperature for the month, not the mean (mean =average of day and night)

September 2015 was warm enough to push it into the record books along the front range. The Denver Metro Area (including Castle Rock) experienced it’s warmest September since records began in the late 1800’s. I have continuously made mention of the strong ridge of high pressure over the western part of the country that continues to steer storms away from Colorado and with them the rain we could so beneficially use right now. How hot was it exactly? You can see in the climate spreadsheet above Castle Rock finished just shy of 4 degrees above average (mean temperature.) This is consistent with what many communities in Colorado experienced, several tying or breaking the record average high.

We began to see some hints that the weather pattern was beginning to change in the latter half of the month. High temperatures began to cool and more clouds were observed. While some places received some decent rain towards the end of September, Castle Rock largely missed out on these storms.
201509_precipsummaryWhile September is usually our driest month of the year, this year September lacked substantial precipitation allowing it to reach the record books as the 4th driest since records began. In the Meadows, we received 3 days of measurable precipitation throughout the month, each day recording about 0.01 inches.

It was very dry, the month finished 1.2 inches below our normal 30 year average in town. October tends to be a bit drier as well but nowhere near as dry as September. With El Nino projected to reach its strongest level ever, we will be keeping an eye on how October 2015 plays out. Please keep in mind, no two El Nino events are the same; so while we remember October 1997 very fondly, it in no way means we could see a record setting blizzard. In fact, with the way the current weather pattern is over the Western United States, we could see a drier than average October. With that in mind, we’ll take a quick sneak peak at what the Climate Prediction Center is projecting for October 2015.

October 2015 Sneak Preview


When I look at the Climate Prediction Center Outlooks for October I see a setup that looks more like what we’d expect to see during an October El Nino year. The Pacific Northwest and most of the Northern part of the country have much greater chances of being warmer than normal for the month. A small bubble of higher colder probabilities exists in New Mexico and Texas, a very typical El Nino October outlook for temperatures.

The precipitation outlook, again very much screams El Nino. A higher chance of wetter than normal weather exists across the Southern part of the U.S. including the Southern and Southeastern parts of Colorado.

I’m analyzing some models to get a better idea of what I think October will look like (I’ve disagreed with the CPC every month since August so I’m not prepared to say whether I agree with them or not in October. Stay tuned, I’ll have this up in a bit!

 October – December, 2015 –>