Two inch rain – drops fall two inches apart. Not to be confused with the mudballs that fall two inches apart on the ground but completely cover your vehicle.
Just enough – just enough rain to splatter your windshield and make mudballs but not enough to water anything
Frog-strangler – a very heavy rain in a short period of time
Goose-drowner – a very heavy, extended rain. According to legend, domestic geese are so stupid that they will stand in the rain looking up to see what is going, and will drown in a down-pour.
the Devil’s beating his wife – the sun is shining while it’s raining.
High-base-b@stard – pilot speak for a high-base thunderstorm, where the bottom is several thousand feet above the ground. The local rule of thumb is if it has been raining for a while (no microburst or any microburst has passed) and you can see through the rain, it is safe to fly through. If the rain is hanging around in the air, or you can’t see through it, go waaay around it.
Heat lightening – At night, the flashes from a storm so far away you cannot hear the thunder or see much of the storm proper.
Cat Rotator's Quarterly 
Caveat on “Goose-drowner”: I learned the anecdote about domestic birds drowning in that way as applying to Turkeys, not Geese. (From my great-uncle, who managed a turkey ranch in the ’50s and ’70s.)
I’ll add:
Six Drops on a Brick — rain just heavy enough for six drops to show on the surface of a normal-sized brick lying flat on the ground. Heavier than a Two Inch Rain, may not be as likely to create mudballs.
My grandfather said goose-drowner, but talked about domestic turkeys. I think in part because he managed a hunting lease, and the wild turkeys were far too smart to do things like that. Domestic geese, on the other hand… It may be more of a regionalism as well, goose vs. turkey. Like my family’s “darker than a thousand midnights at the bottom of a cypress swamp.”
We always called it a toad-strangler, but the general idea is the same.
Also, when it had been raining steady for a couple days the saying was, “nice weather… if you’re a duck.”
And heat lightning refers to two things here. 1) as you say, lightning you can see the flashes of, but not hear the thunder and 2)summer thunderstorms with lightning, usually wind, but no rain. Very bad to start fires.
I was wondering if heat lightning was actually different from normal lightning or not… I guess with the whole no-real-mountains* thing, you can see a LOT further. Explains why we get such pretty lightning storms– almost every day this week!– but so very little thunder.
I think we may have gotten your rain, though. Not sure if flood warnings more days than not is standard for the rainy season, here.
* My baseline is screwy. I grew up in the crevice between mountains. This cute little ridge they have in El Paso? The hill where we put cows in fall, that’s “right behind the house,” is bigger– and has more whatever you call the little hills that are on a big hill to make a mountain. The baseline elevation is higher than the pass to my parents’ place, but it has all the way from Cali to reach it, not less than a hundred miles. 😀