The Weatherstation

The data shown on these pages comes from various sensors, sited at an altitude of 260m (860ft) above the village of Pontrhydygroes, Ceredigion, approximately 12 miles (20 km) ESE of Aberystwyth. It is updated 24 hours a day.

The server is currently a Lenovo ThinkServer TS140 running Ubuntu Server 20.04. This is both the web server, and the computer which gets the data from the sensors, processes and graphs it. The graphing is done at 10 minute intervals. The current data is gathered at 2 minute intervals.

The weatherstation came back into action in September 2021 after a break of four years, when the previous Technoline (LaCrosse) WS-2307 failed. Archived data up to Septe,ber 2017 remains on the site.

Until September 2010, the weatherstation was a LaCrosse WS-3600. On 27th August, the outdoor thermometer/hygrometer failed, ending over five years of almost continuous records. This was replaced on 12th October 2010 by the present weatherstation, and the records combined. As a result, however, there is no archive for September 2010, and temperature and humidity data are missing between these dates. Rain and wind data however continued to be recorded until 7th September, when the weatherstation was removed for (ultimately unsuccessful) repair.

Sensor equipment


The server receives data from sensors directly via 433 MHz wifi, using a Software Defined Radio (SDR). intercepting signals using the rtl-433 scripts which are available directly from the Ubuntu repositories. Using this has huge advantages over using a weatherstation wired directly to the server:

Temperature and Humidity

The two sensors currently in use report themselves to be Ambientweather-F007TH. One is outside, against the wall of an outide (unheated) building. Yhat's not ideal; I need to build a screen. It is, however, in a location that the sun never gets to, except maybe in the late evening of the longest of summer days. The second one is in a shaded part of the glasshouse

Rain gauge

This is a TFA Dostmann DROP rain gauge. This seems to be good, though obviously made for an imperial measures market. One drop of the gauge is 0.254 mm (exactly 1/100th of an inch).


This is the only sensor data that doesn't come via 433MHz. As far as I can tell, no-one makes a 433 MHz pressure sensor for weather. In a way, there's no point, because pressure is the same inside a house as outside. So instead I export data from Home Assistant, which I have running on a virtual machine on the same server. The pressure data comes from a Xiaomi Aqara Temperature/Humidity/Pressure sensor which is located indoors.


I do not currently have a working wind sensor. I am not aware of a stand-alone 433MHz anemometer and wind vane which will work with rtl-433.I've tried to get my old Technoline one working, but without success so far.

The official definition of an "absolute drought" is 15 consecutive days with no measurable precipitation ( The word "Drought" is displayed when this occurs, though as this rain gauge measures in 0.52mm increments, this may not strictly be correct. Other words used, such as "Dry", "Very Dry" and "Parched" are my interpretations.

Occasional obvious bad data for all measurements taken by the outside unit is returned by the weather station. When I notice these, I will edit the log files as appropriate.

Disclaimer: I take no responsibility for the accuracy of any data on this web site; any use you make of data from this site is entirely at your own risk!

The Software

Apart from the rtl-433 decoding software, and the Home Assistant data, all software to process the data is written by me, over a period of many years. As a result, it's not necessarily the tidiest of software projects. It's a collection of Bash, Perl and PHP scripts.

The Webcams

There is not currently a webcam attached to the weatherstation. I have been given an old Android phone that I intend to try to use for this.

All processing of images is done using ImageMagick. I check the average pixel intensity, and the standard deviation. If these are below a threshold value, I do not upload the resulting image to the web site (and the message "Light too poor" will be displayed). The result of this is that the Fuji camera will tend to operate only whilst the sun is above the horizon. In direct sunlight, the image may be washed out, and poor light will be detected. Exact operation times depend on weather conditions, naturally.

Photographs are taken every 2 minutes. Every hour (except when too dark), the last photograph is archived. The previous 20 archived photos are kept and can be viewed using the Prev/Next buttons on the webcam page. The 14:00 photo is kept for a number of additional days.

Sun and moon data

Sun and moon data are calculated using the Perl modules Astro::Coord::ECI::Sun and Astro::Coord::ECI::Moon, available from the CPAN Perl archive (sun, and moon). The data displayed are for the village of Pontrhydygroes, Ceredigion. In the tables, the next event is highlighted in red. For accuracy, see the documentation in the CPAN archives. On a clear evening, light for walking in the open hills is generally adequate up to the time indicated by marine twilight.

Browser compatibility and standards compliancy

These pages all comply with the World Wide Web Consortium (W3C) standards for XHTML 1.0 transitional and CSS. They have been tested, and found to work correctly, in all popular modern desktop browsers. There is an element of responsive design which should help with mobile browsers, but the main table still needs to be worked on in this respect.

The graphs on the year archives pages do not look good; I still have to work on these.


Where does the name come from?
Tywydd is Welsh for Weather.
Why do some numbers not seem to add up?
On the current weather page, some data is read every 2 minutes, and some every 10 minutes. You may be noticing that difference. For example, when it starts to rain, you might see the figure 0.5mm recorded for rain in the last hour, whilst the other box tells you it's dry. Check again a few minutes later.
When I click on a graph for this month, why does it give me last month's graph?
For the first day of a new month, the month graphs are not updated. There is no point; you can always check this month so far by looking at the graphs for today. Similarly, for the first hour of the day, the day graphs are not updated.
I don't like the colours you've used!
For the current weather, all the cell colours except for the wind are weather dependent. Check back when the weather's changed, and see if you like it then!
There is no time given for astronomical twilight. Why not?
Pontrhydygroes is sufficiently far north for there to be just over two months in the year (around midsummer) when astronomical twilight lasts throughout the night. The display reads --:--:-- when this happens.
Can I have your programs?
Yes, but unless you're a programmer, you probably won't either understand them or be able to get them to work. Also, they will only work under Linux/UNIX as they are at the moment, and I have no intention of making them work under any other operating system. Drop me an email if you want them.
Are the pages updated 24 hours a day?
Generally yes, though I don't guarantee it. The server is connected to a UPS, which should avoid problems with short power outages.
How accurate is the forecast given on the current weather page?
It really isn't terribly accurate. It is from the weatherstation itself (i.e. not my calculations), is apparently based on pressure trend and nothing else, and could be improved. I might write something to give a little better forecast, but pressure-based forecasts alone are never going to be very accurate.
After checking your site, I decided it would be a good day for <something>. But it wasn't, and as a result, (I got very wet | I got lost in the mountains | something really bad happened).
That's your problem. See my disclaimer above.
Can I link to your site please?
Of course! Please link to (you don't need the rest of the URL). I'd also appreciate it if you'd drop me an email to say you've linked to me!

Angharad Shaw