Definitely possible, but that area of the country is extremely dry compared to up here. While I always see water dripping from tailpipes on any car/truck with a cat, I never see just a brief blast of white when starting - even on really humid, cold mornings. Up here in the spring, fall, and winter, after the vehicle is running 10 seconds or more, a constant white fog will come out. That's just warm moist air meeting cold air and condensing into droplets. Colder it is outside, the longer and thicker the fog.
I've seen a brief blue blast from my truck starting around 50k miles, but an oil catch can has totally eliminated that. It's possible you have just a small bit of coolant leaking into one or more cylinders over time - not enough to happen when the engine is hot. In that case rather than go through the trouble of yanking the heads and all that, I'd just dump some K-Seal or Bars Leak in the radiator and call it a day.
Are you in the valley, or up in the mountains?