Waking up this morning, I noticed a big difference compared to yesterday: it was still quite dark and the sky was covered with thick clouds, whereas yesterday it was bright and sunny! The dreary gray sky did not stop me from getting up. I had to get to work and there was still plenty of light for me to go about my daily activities. For the plants in my garden though, the difference in sunlight has a much bigger impact than it does on me!
The sun continuously emits radiation across a wide spectral range. Which part of that reaches earth depends strongly on where you are and what the weather is like. In fact, the spectrum remains much more stable than the amount of radiation. The spectrum varies slightly depending on location and weather, but aside from dusk and dawn, it always looks similar, ranging from UV to IR radiation.