Monthly temperature chart

A year of weather at home: Temperature

Lo and behold, we now have a year and a bit of weather station data, collected at home in Sun Valley. We derive an enormous amount of utility and enjoyment from the weather station (being unashamed weather nerds), and I am very excited to get my hands on a good chunk of data to visualise. I used R for the charts in this and the following two posts. I haven’t got my head around ggplot2 (one of the powerful plotting packages built for R) in a very meaningful way yet, but I’m using the weather data as a fertile field for my plotting experiments. The charts I’m going to show are using 12 months of data, but not a calendar year. The data runs from the start of December 2013 until the end of November 2014.

Monthly temperature chart
Monthly temperature chart

I chose to plot the temperature in a radial chart. Each axis represents a month, and the minimum temperature for the month is shown in yellow at the centre of the axis. The year’s lowest temperature was on 7 July, and was recorded as 3.5 degrees. That morning Tony poured warm water into our little pond at the front door, to provide some winter cheer to the tadpoles, and my car was covered with a coating of ice. I am depressed – just looking at this photo – by how gloomy it is at 7.30 am in winter.

Ice on my car on the coldest day of the year
Ice on my car on the coldest day of the year

The orange line is the average temperature recorded each month. It lies around a dotted grey line with a label of 17.6 on it; this is the average temperature for the year, and is quite close to the annual average temperature that I generally hear bandied about for Cape Town of 18 degrees.

The red line around the outside of the chart shows the maximum temperature each month. The maximum for this year of data was a round 35 degrees recorded in January.

I haven’t split the temperature chart seasonally, but as a general rule of thumb in Cape Town (that I think I got from Lawrence G. Green, rather than the equinoxes and solstices) you can think of winter as starting on 15 May, spring on 15 August, summer on 15 November, and autumn on 15 February (though personally I think autumn is short and only kicks in during mid to late March). So if you imagined drawing an X over the radial chart, summer would be between the upper two arms, and winter at the bottom.

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Lapsed mathematician, creator of order, formulator of hypotheses. Lover of the ocean, being outdoors, the bush, reading, photography, travelling (especially in Africa) and road trips.

2 thoughts on “A year of weather at home: Temperature”

  1. Hey Clare,

    Came across this blog as I was looking for some interesting ways to plot and visualize weather data. Nice plot you have there for the min, mean and max temps. I’m assuming you did it in R using ggplot? Anyway, if you’re interested in doing some other types of plots with your weather station data, you can check out a blog I run with a colleague of mine (we’re both weather enthusiasts) –

    Would be real nice if you shared some of your code on here as well for us weather geeks! 🙂


    1. Hi Jason
      It is so good to hear from you! I will check out your blog in detail this weekend and send you some code. It’s not fancy – I modified a function that does radial plots – but am happy to share. I knew there had to be weather enthusiasts using R somewhere on the internet but never found the search terms to bring me to them. I’m glad you found me!

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