This replaces the previous solar activity watch, which was issued last month when the sun took off its sunglasses.
Children's drawings may stereotypically personify objects that are not living, even such as planets or stars. In children's drawings, the Sun is normally drawn smiling. This comic acts as if this smile was an actual thing that the Sun (which is sentient in this comic) has. Apparently, the emotion that the Sun is expressing can signal imminent solar flares and coronal mass ejections, hence this official announcement of a warning.
The title text indicates that the prior change that provoked a warning was when the Sun's sunglasses were removed. The Sun wearing sunglasses is a further (possibly paradoxical) element of personification often added to such an image of the Sun. Randall has previously refered to the Sun's sunglasses in comics such as 1733: Solar Spectrum and a couple of What If? articles.
The removal of eyewear is used in the "Deal With It" visual meme or as part of the various other tropes that reflect a change in attitude. Another interpretation could be that it is referencing Minesweeper, where the Sun puts on sunglasses when the game is won and takes them back off when the game is reset, e.g. there is more danger.