Could there be a correlation between temperature and background radiation?

Perhaps I am trying to force some interpretation, but I have noticed that from the change in temperature indicated in the image (the minimum temperatures become lower), I register a slight but noticeable increase in the background radiation.
I have thought that it may be some natural element, which emits more radiation with the decrease in temperature, or the change in the position of the earth with the change of season.
Another possibility, perhaps more likely, is that the temperature affects my geiger counter.
Something that I must clarify is that my temperature records are very bad, first because at a certain time of day the sun shines directly on the sensor (placed outdors) and that causes the peaks, and second because I placed the 5v transformer too close to the sensor, transferring heat to it and generally increasing the temperature by 3 or 7 degrees. Excluding that, the conditions are always the same, and I can confidently affirm the reduction in temperature.

It could be due to changes in the rate of outgassing from materials in the area near your probe, chiefly of radon.
 

Like FSM19 says could be an out gassing issue, if you have a glass tube it might be responding to UV light. Best practice for placement is under a shaded cover so that you prevent misreadings due to direct sunlight. Similar like how you need to install a precise temperature sensor.

In short, keep it out of the sun

Had just that issue with a couple of glass tubes. My main probe is now enclosed in a watertight box covered with grounded adhesive copper foil. Means its also shielded from RF which was an issue for me as  I am a ham radio operator.

My tube is a shielded SBM-20, which is inside a black plastic geiger counter, which together with the ESP8266 are in an opaque case, inside the wooden cabinet, under the TV, connected to the USB port of my modem (which I think , it is one of the most filtered usb outputs that can be found)... So yes, it does not receive too much light 
I am seriously considering that it may be radon gas, which I have never heard of before, since I am not someone who is very assiduous to ventilate the house, less in winter...