Why is the month of Aprill masculine?

Question

In the first line of the General Prologue of The Canterbury Tales, the month of April is given a masculine pronoun:

Whan that Aprill, with his shoures soote

Why is this?

Answer 1

There have been a couple of different explanations given for this, but the upshot seems to be that there's nothing particularly significant about the masculinity of April - it was more a product of the way language was used at the time than any kind of symbolic statement about masculinity.

In his Notes to the Canterbury Tales (2014), Prof Walter Skeat says that the masculinity of Aprille is derived from that of the Latin Aprilis. Latin was of course much more widely used, especially in literature, in Chaucer's day.

However, in his notes published here and based on those of Alfred Pollard, Prof Edwin Duncan cites Skeat and then points out that:

as his in Chaucer's time was the neuter, as well as the masculine, genitive, there is no evidence that Chaucer here personified either the month or the wind as a masculine.

The reason why "his" was used as a neuter pronoun is that the word "its" didn't exist yet. According to Etymology Online, the neuter possessive pronoun "its" dates back to around the 16th century, well after Chaucer's time. (Thanks to @GarethRees for pointing this out to me.)

Answer 2

This is possibly a reference to astrology. In western astrology, April is regarded as a masculine month.

April is the month of Aries, The Ram, a masculine sign. It is ruled by Mars, a masculine planet.

As astrology was more highly regarded in Chaucer's time than today, he could well be making a reference to April's astrological masculinity.

However, to be sure of this as an explanation, a reference to a feminine month using feminine pronoun is needed. I can't immediately think of such a reference.