Yes the lager needs to be warmed up a bit before racking. Excessive aeration also seems to cause diacetyl, beers brewed with Yorkshire Stone Squares seem to have it.
That is one reason an ale should sit in primary for two weeks: the yeast cake will clean up the diacetyl and other faults. Since in summer the temperatures may be too hot to allow this (autolysis is a danger in summer) summer brews may have some diacetyl.
For hot weather brewing I suggest dropping (racking off the yeast with some aeration) at day two then bottling at day 7.
As a Lager Brewer, may I humbly suggest an amendment to JM's post (quoted above)...
Yes to primary ferment the Lager at a low temp with a good quality Lager yeast...
Don't rush the Lager!
Give it a week in primary (at least). Don't rush it!
Rack to secondary and cold condition for at least 3 weeks (no higher than 8C) Don't rush it!
If you drop and bottle within a week, you get a very green lager that takes a long time to condition in the bottle. Lagers prefer to cold condition in bulk - as the Germans did! Leave them in secondary fermentation where the good quality yeast that's still in suspension can get to work on conditioning the more complex fermentables in the Lager, without increasing autolysis risk that would occur if it was left in higher temp primary on the yeast cake.
As for aeration after Primary fermentation - Good Luck! :blink: I don't want to get into a "how and why we should drop worts" argument, but I have never done that and my lagers are well received by all who drink them!
Palmers chapter on Lagers is a good reference, but I tend to get better results by not stuffing around with the wort - it's like any champion product - the more you mess with it, the more likely you will not achieve what you originally wanted.
Just keep the temps down, use good yeast and diacetyl rest if necessary, but most of all - be patient!
Ein beer bitte!