Green’s Dictionary of Slang

1. a flower [rhy. sl.].

1944		Maurer & Baker ‘“Aus.” Rhyming Argot’ in AS XIX:3 192/1: Cobar Shower. A flower.
1950		Sun. Herald (Sydney) 5 Nov. 95/4: ‘Cobar shower’ for flower [...] In so far as we use it in Australia, we mainly apply it to a dust storm.
2002		Pete’s Aussie Sl. Home Page 🌐 Cobar shower: a flower.

2. a dust storm [pun, i.e. it’s very dry].

1914		Sthn Record & Advertiser (Candelo, NSW) 17 Jan. 1/2: During a western dust storm the other day a flock of 80 sheep were smothered. That’s what is known as ‘a Cobar shower’.
1915		Nat. Advocate (Bathurst, NSW) 21 Jan. 3/4: Bathurst’s share of the seven plagues spreading over the world came in the shape of a ‘Cobar shower.’ Bathurst is the last place one would come to for a ‘Cobar shower.’ It is said that about soo miles further west the red dust is a common plague and that a regular record is kept of the number of feet of Cobar rain that fall in the season.
1935		Nat. Advocate (NSW) 23 Mar. 2/3: The arrival of a ‘Cobar Shower’ on Thursday evening perturbed Bathurst housewives for it left a thick coating of dust in its trail.
1944		Maurer & Baker ‘“Aus.” Rhyming Argot’ in AS XIX:3 192/1: Cobar Shower. [...] This term is used in Australia, never to mean a flower but a dust-storm.
1953		Gilgandra Wkly (NSW) 25 June 1/4: [W]hen some visitors came to town they commented upon the uneven appearance of the main street and asked had a Cobar shower done the damage.
2002		Sydney Morning Herald 28 Nov. n.p.: Cobar shower [...] a dust storm.