After reading the primary sources related to red snow and rain, there are at least two different types of physical events occurring. One is clearly associated with falling objects from outerspace and the other with blooms of terrestrial organisms.
Reports on it typically ignore the observed cases of "falling red snow"; falling red rain (sometimes with coagulated texture) is not even associated in most reports claiming terrestrial origin. Unless they want readers to assume that these organisms find their way high in the atmosphere, inland, and hundreds of miles from the nearest glaciers or ocean.
Now let's assume Chlamydomonas nivalis and related organisms are the primary terrestrial source of red snow. Now, we are still missing an explanation for the falling red snow and rain, most of which are connected with fiery meteors as Chladni clearly shows.
And it is know that red coloration occur in the comets, asteroids, and moons of the solar system.
Thus, even if speculative, it is theoretically possible that Francis Bauer in 1819 drew extraterrestrial micro-organisms, fallen as layers of snow from cometary material in the Baffin Bay area, perhaps a week or so before the arrival of Captain Ross.
Francis Bauer's Microscopical Observations on the Red Snow
Might this be what we find within the ice of moon Europa?
Image Source: Microscopical Observations on the Red Snow, 1819.
