Saab: 1984 900S -- brake caliper seized in cold weather

I recently bought a 1984 900S to replace my old 1984 900S, which met an
unceremoniously early demise when I was broad-sided by someone who ran a
stop sign (the car was unfortunately totaled).

This morning, the front right brake caliper was temporarily seized up. The
car moved, but it didn't roll very well. I drove a few blocks hoping it
would release once it warmed up. When I pulled over, the caliper was
smoking. I started the car up again, and pumped the brakes and engaged and
disengaged the parking brake a few times, and the caliper released.

We've had the coldest weather of this year in Rhode Island (teens F at
night, forecast to be in single digits F the next few nights). My old 1984
900 S never had this problem, but this is the coldest it's been since buying
the current car.

Any ideas why this might have happened? Or suggestions for how to avoid
happening again?

As always, any information much appreciated!

Thanks,

-jw
--
1984 900 S
198K miles
Rhode Island, USA

> WD40 is not a lubricant. It's a cleaner. Use a lubricnat after you use 

???

<from wd40 webpage>
CLEANS: WD-40 gets under dirt, grime and grease to clean. It also
dissolves adhesives, allowing easy removal of labels, tape, stickers,
and excess bonding material.
DISPLACES MOISTURE: Because WD-40 displaces moisture, it quickly
dries out electrical systems to eliminate moisture-induced short
circuits.
PENETRATES: WD-40 loosens rust-to-metal bonds and frees stuck, frozen
or rusted metal parts.
LUBRICATES: WD-40's lubricating ingredients are widely dispersed and
hold firmly to all moving parts.
PROTECTS: WD-40 protects metal surfaces with corrosion-resistant
ingredients to shield against moisture and other corrosive elements.