It means that there is a chill in the air, but how it originated I don't know.

One for Quizmonster.

It probably derived from cockney rhyming slang.  Parker Bill - Chill, or something like that.

A 'parkie' is another word for a park-keeper.

There's some (to me) unexpected information at http://www.urbandictionary.com/define.php?term=parky&r=f

It's definitely not Cockney - Yorkshire normally claims it as theirs but I've heard it in Durham/Cumbria  too. Don't know where it came from originally though.

Bit of a dodgy reference there, E! I've certainly never heard that interpretation before. 'Parky', meaning 'cold',  has been around since the late 19th century. I'm not sure about north of England dialect, but certainly the word 'park' in Scotland does not usually mean that pretty green area in a town centre but rather an open field. (It's often used in the names of football stadia, too.) Consequently, I've always assumed that it suggested the chill one might expect to experience if standing in an exposed field...ie parklike/parkish.

I'm with Quizmonster here. I've always assumed it meant being cold as outdoors (i.e. in the park). In fact, if someone walks out of a room without closing it behind them, others shout (here in Scotland anyway) 'Were you born in the park?'

It comes from the eskimo word for 'coat' which is parka.

this is also where we get the name for our big zip-up coats - Parkers .

My parents were from the south-west London suburbs - Chiswick and Richmond-upon-Thames - but "Parky" was a word in our vocabulary, in its meaning of "Chilly". We also used "Parkie" (note spelling) as a contraction of "Park-Keeper": the groundsman in a public park.