How does "bluebird weather" get its name?

In Maryland and Virginia, bluebird weather is a brief period of warm weather in autumn.

https://www.waywordradio.org/bluebird-weather/

How does “bluebird weather” get its name? This article explains the spiritual meaning of bluebird. I don’t see how it is related to “bluebird weather”.

Bluebirds are known as “Spirit Animals,” who carry messages from the spirit world. The bluebird meaning is happiness and pleasure. Any positive sentiment is always attached to the bluebird; whether it is happiness, pleasure, prosperity, or good health.

https://www.guardian-angel-reading.com/blog-of-the-angels/bluebird-meaning/?media=BLOG&campaign=bluebird-meaning

It apparently derives its figurative meaning from a poem as explained below:

Figurative use in bluebird of happiness is from 1909 play romance "l'Oiseau bleu," literally "The Blue Bird," by Belgian dramatist and poet Maurice Maeterlinck (1862-1949).

(Etymonline)

Its usage is not confined to weather as suggested by a BusinessToday

Bluebird has been increasingly used in corporate circles in the past few years.

Usage:

The company's game plan to widen its customer base ensured some bluebird sales.