September 2023 Graphical Weather Review: A quiet transition from summer to autumn, except for one day of torrential rain

September 2023 was an overall warm and dry month in Boulder, but technically we did finish with above normal precipitation. Almost all of that came on a single day as a result of a locally heavy thunderstorm. We’re yet to see a real autumn storm in the Front Range and as a result it hasn’t snowed yet outside of the Mountains, which is fairly normal with our average first snowfall not coming until mid October. Here’s a quick and colorful graphical recap of our weather during September and how it relates to climatology.

September 2023 Recap Graphics:

How does September 2023 fit into the last 74 years?

How does September 2023 fit into the last 12 months?

Updated 2023 90° Day Tracker

Drought Tracker (as of October 3rd)

Our top posts of September 2023

September 2023 retold via our Twitter X timeline

Interesting virga at sunset last night 🌄 #cowx pic.twitter.com/8TZJIuuX6C

— BoulderCAST Weather (@BoulderCAST) September 1, 2023

For the third day in a row, #Boulder Airport has hit 95°F on the dot. Not too bad out there though as dewpoints are only in the 30s. It's a dry heat they say! 🔥🌞 #COwx pic.twitter.com/HulDBQZMyE

— BoulderCAST Weather (@BoulderCAST) September 1, 2023

It is quite cloudy this afternoon. They may be enough to prevent us from getting to 90° but it will be close. 87° now… #cowx pic.twitter.com/hAsbWBrsNh

— BoulderCAST Weather (@BoulderCAST) September 2, 2023

Mountain wave crashing down the east slopes tonight — and it's only September 4th! Gusts of 50-60+ MPH occurring just up the hill! #COwx #Boulder pic.twitter.com/mi8VEzJiC6

— BoulderCAST Weather (@BoulderCAST) September 5, 2023

🍁 Canada just keeps putting out the smoke & we just keep dodging it here in Colorado. We've been pretty lucky this summer to avoid it most of the time. With the seasons changing we'll soon be getting more Canadian cold fronts & our luck may run out…🔥 #smoke #COWx pic.twitter.com/YPDnrV16NG

— BoulderCAST Weather (@BoulderCAST) September 5, 2023

Hurricane Jova has weakened from Category 5 to 4 today as she/he/it heads out to sea away from Mexico! #Jova pic.twitter.com/hgSjxlM1LK

— BoulderCAST Weather (@BoulderCAST) September 7, 2023

That blue sky this Saturday morning! 😍 #cowx pic.twitter.com/rtJYdlGha5

— BoulderCAST Weather (@BoulderCAST) September 9, 2023

Following an overnight cold front, low clouds and Canadian smoke hang over #Boulder. Also seeing some occasional mist! 🌫️ #cowx pic.twitter.com/tqUSAk5MFG

— BoulderCAST Weather (@BoulderCAST) September 10, 2023

The sun is out and we had an overnight rainfall total of 0.43"! #cowx pic.twitter.com/eb7hDWV9zL

— BoulderCAST Weather (@BoulderCAST) September 11, 2023

3:00PM: Very heavy rain and small hail falling in south #Boulder, and also along much of Hwy 93 heading south! #cowx pic.twitter.com/HiPrabzkVn

— BoulderCAST Weather (@BoulderCAST) September 14, 2023

❄️ Big wet flakes falling again in RMNP atop Trail Ridge Rd! #cowx pic.twitter.com/0m64RS8R5v

— BoulderCAST Weather (@BoulderCAST) September 14, 2023

Torrential rain and pea sized hail from earlier… #cowx pic.twitter.com/g9quRiuUxk

— BoulderCAST Weather (@BoulderCAST) September 14, 2023

🤯 1.61" in our rain gauge as of 8AM!

📏 However, 1.76" was the official amount for #Boulder

💣 1.54" of that fell yesterday, the largest 1-day precipitation total for the city since the March 14, 2021 Bomb Cyclone which put down 20" of snow: https://t.co/UX3NT2WWjo #COwx pic.twitter.com/HHBApoML83

— BoulderCAST Weather (@BoulderCAST) September 15, 2023

Another beautiful day in the Bubble! 😍 #cowx pic.twitter.com/FkfWQxyPKq

— BoulderCAST Weather (@BoulderCAST) September 17, 2023

The extended forecast stays exceptionally quiet across the Front Range. There are still no major cooldowns, accumulating snow or even frost in the pipeline — something that is typical for El Niño. This & more in today's *Premium* weekend outlook: https://t.co/9g853Srupt #COwx pic.twitter.com/G8GQ5Dq5wd

— BoulderCAST Weather (@BoulderCAST) September 21, 2023

Happy first day of Fall! 🍁🍂🎃 #COWx pic.twitter.com/NLq78FebDC

— BoulderCAST Weather (@BoulderCAST) September 23, 2023

So about that sunset tonight…🌄 #cowx #denver pic.twitter.com/4dIOu1xidg

— BoulderCAST Weather (@BoulderCAST) September 27, 2023

🥶 Typically our first "frost" (32°F or less) comes during the first week of October. However, with an active El Niño (like it is now) it often comes about a week later. Still ZERO indication of frost in the 10-day forecast.. #COwx #Frost #Boulder #ElNino pic.twitter.com/KpdH2rnHWV

— BoulderCAST Weather (@BoulderCAST) September 25, 2023

🌲🔥💨 Intermittent smoke will continue to invade the Metro area the next few days thanks to several fires burning upstream in the Four Corners region & also a controlled burn near the Springs. Expect limited sight lines to the Mountains, but OK air: https://t.co/BMCFXMPCcH #COwx pic.twitter.com/siMrKqQ6IG

— BoulderCAST Weather (@BoulderCAST) September 28, 2023

A wispy afternoon. Don't look up! #cowx pic.twitter.com/mtOQ5t1xFK

— BoulderCAST Weather (@BoulderCAST) September 30, 2023

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BoulderCAST Team

This post had major contributions from at least two members of our team. The more meteorologists the better, right?

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