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Logging Started On: Jan 6th 2015
Logging Stopped On: May 17th 2015

Ambient Temperature High: 96.8° F
Ambient Temperature Low: -0.9° F

Relative Humidity High: 80.3%
Relative Humidity Low: 18.7%

Dew Point High: 70.9° F
Dew Point Low: -13.7° F

Processor High: 138° F
Processor Low: 39° F

Graphics Chip High: 142° F
Graphics Chip Low: 50° F

Logic Board High: 129° F
Logic Board Low: 37° F

Hard Drive High: 122° F
Hard Drive Low: 36° F


Machine: Late 2006 iMac 20"
Processor: Intel Core2Duo 2.16 GHz
GPU: ATI Radeon X1600
Hard Drive: 80 GB
Wifi: 802.11 a/b/g/n
Mac OS X 10.6.8 (Snow Leopard)
Apache 2.2.24 / PHP 5.3.26 / MySQL 5.5.29

Official “Limits”

Operating Temperature: 50° to 95° F
Storage Temperature: -40° to 185° F
Relative Humidity: 5% to 95%


For questions, comments, suggestions, and general feedback, you can contact us via:


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Dew Pt
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Hard Drive

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Coldest 24 Hour Period - January 8th, 2015

Daily Ambient Temperature Range


Practical Design Group has donated an awesome USB Thermometer & Hygrometer (THUM) to this project. As you can see, it works great! The ambient temperature, relative humidity, and dew point readings are coming from the THUM.

About This Mac

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ColdMac is an old Apple computer, that lives in my shed, and tracks it's own internal and external temperature, and also hosts this webpage about itself. This year, it's also running Seti@Home and a few other BOINC projects at 50% CPU power, to "keep warm".

The shed this Mac lives in is very cold. It is not insulated, the door has no seal, and there are two vents in the walls. So while there is a very limited amount of thermal protection, it's generally within 5 degrees or less of the actual outside temperature at night. During a sunny day, the she can warm up much warmer than the outside temp.

This Mac is a 2006 intel Mac. It is loaded with internal thermal sensors. I also use a USB THUM sensor to get ambient thermal readings. Every 10 seconds, a shell script polls all sensors, and records the values into a MySQL database.

The hardest part of making this project is always the charts. The rest of the site is actually pretty simple components, that are pieced together in an interesting way. But making the charts has always been a problem. I used flash charts in the past, but I have since switched to google HTML5 based charts so you can see them on mobile devices. Setting them up is not nearly as easy as google thinks it is, but with persistance, they do work.

Previous Winters