[QUOTE David E. Ross
Climate: California Mediterranean
Sunset Zone: 21 -- interior Santa Monica Mountains with some ocean
influence (USDA 10a, very close to Sunset Zone 19)
Gardening pages at http://www.rossde.com/garden/[/i][/color]

What type of cymbidium do you have? While cold tolerance does depend
on the species in the plant's background, the bulk of the large
standard cymbidium hybrids should do fine without much protection in
Zone 10. My temps can get down to 30F briefly on winter nights and my
cymbidiums are unaffected. As for dividing unless the size is an issue
for you I wouldn't bother about it. Larger cymbidiums generally have a
better chance of flowering after repotting than smaller divisions.[/quote]

I have to echo David E. Ross on this point.
It all depends on what type of Cymbidium you are growing:
Temperature requirements for Cymbidium orchids range from cool
to medium, i.e. between 10 and 30 degrees Celsius (50 to 85 °Fahrenheit)
is ideal. DO not stress your Cymbidium, in the latter part of summer it may
be wise to have the temperature drop at night to force the orchids into
bloom. This temperature drop is required to maximize flowering else the buds
will turn yellow and drop down if it is too hot at night in summer.
I grow mine both indoors and outdoors.
All of them have bloomed this season.