It occurs to me that, by the laws of Hermetic magic, Creo Auram spells can make rainfall, but the resulting water fades when the spell ends. If I'm reading that correctly, an Auram spell needs to be a ritual in order to create rain that will properly water a farm. That I do not mind.
What I do mind are the core book's example spells. Clouds of Rain and Thunder is probably what a new player will choose when they want a magus to command the weather... except then that magus' rain will slake nobody's thirst, rejuvenate exactly zero dry riverbeds, and make some stalks of barley very confused, followed by being very dead. I can understand Clouds of Rain and Thunder not being a ritual if it is meant as a combat spell, to disrupt a battlefield... except then the spell description suggests no mechanical effects for people fighting in the storm. Clouds of Thunderous Might sounds more like the intended effect our magus is going for, forcing existing, "real" meteorological phenomena to behave like a storm... except that doesn't actually specify that it will be raining! For all the magus knows, it will be a very dry and gritty vortex that causes widespread destruction and no rain whatsoever.
My question is thus; For a magus fresh out of Gauntlet whose player wants to be able to cast a benevolent rain-making spell, what would our more experienced members suggest?
Interesting and useful to know that Rego effects can do that! I was unsure that Rego could properly "teleport" objects outside of cases such as Leap Of Homecoming. I was hoping to make a character who commands the weather, but if that isn't an option I could do it with Aquam too.
Also, a starting character can have rituals, right? I seem to recall the example Bonisagus in the core book knowing Purification of the Festering Wounds.
Perhaps a Rego Auram spell could cause existing clouds to produce real rain?
Harvest the Bounty of the Clouds
Range: Sight, Duration: Sun, Target: Individual
This spell causes existing clouds to produce rain for the duration of the spell. Since the water is not being created by the magic, this is real rain that will water crops, fill streams, etc.
Base 4 (control air effects in a forceful but calm way) + 3 (Sight) + 2 (Sun)
That's the thing, I desire a starting character to be able to do this with the rules as written. Clouds of Thunderous Might does not actually say it produces rainfall in the description, only that it makes a storm- so it is likely up to Game Master fiat wether or not it does. Casting the spell in January COULD make freezing rain, or it could make snow. Casting the spell in a desert may very well create a sandstorm, the opposite of the intended effect. Worst of all, there may simply not be enough clouds within line of sight to form a storm front.
With Clouds of Thunderous Might, we run into the old problem of effects based on weather or time being dependent on the Game Master wanting the players to succeed; the same with lycanthropes and phases of the moon. Am I being too paranoid, assuming an adversarial Game Master?
If you cast Clouds of Thunderous Might during a time where rain usually falls on local crops, and rain doesn't fall, you should assume that finding out who "cursed the sky" is your adventure. Gather your priests, your demon-hunters, those familiar with Auram magic and those familiar with the ways of the weather fae, and figure out why the natural order is disrupted.
Outside of the usual rainy season, you don't want to rain on or near your crops. You don't need to rain on unplanted ground. You don't want to rain too early and kill the plants. You don't want to rain too late and rot the plants. So rainwater in January isn't an issue where you expect snow in January (no crops to water!), and in the desert in January, it's likely the rainy season.
In Egypt, where it rarely ever rains, no one expects it to rain on the crops anyway; they get their water from the Nile, and raining on their plants is counterproductive.
Drinking water is a tougher issue, and I wouldn't make it rain to get that (might cause flash floods in the off-season); I'd pull it from the ground instead.
There is actually spell called The Sudden Well in Against the Dark that creates a well-shaft. While quite suitable for dropping bad people 100+ feet into the earth, it's also useful in the capacity you describe - perhaps in combination with an InTe(Aq) spell of some kind to search for water beneath the earth, and some sort of ritual (Muto or Creo Terram?) if you'd like to make the well permanent and structurally stable.
Hmm. I believe part of the goal was to avoid ritual magic.
Regarding the topic, Creo Auram and dry crops (not that we've been off base, but I had a question based on those specific things), if I use Creo Auram to make a storm(dur:diam), and it rains in a field, is the field dry three minutes later? At first it seems like a no-brainer, but if I use Creo Ignem to create a fire, Bob the Grog doesn't heal the burn; Creo terram swords don't heal the stab wounds. Creo Auram lightning bolts don't undo their damage after their duration. All obvious, but... Is the rain falling from the sky part of the storm, or a side effect of the storm being in the sky. The closest counterpoint I have is the creation of insects in Transforming Mythic Europe involves using one temporary creo spell to 'create' a permanent effect. I can actually see this argument both ways.
I think the point of guidance here is the mighty rushing torrent of water, which states that when the spell ends the water is gone but any combat effects (people knocked over, injuries, extinguished fires) persists. So your storm can cool the air, ruin hairdos, extinguish flames, make quick drying mud cake to everything during the storm, perhaps cut a small ravine where the torrents of rain flow to, but not leave water behind.
The insect spell specifically says "things generated by magically-created animals persist even when the spell duration ends". So it may well be an exception to the standard rule. (Even so, I think that spell may be a misreading of Creo Animal -- the example in the main book has horse-apples persisting but only after a Moon duration, and only because the horse has been fed on mundane food in the meantime.)
I would say that rain (or snow, or hail) falling from the sky is to the medieval mindset a necessary part of the definition of "storm". So the physical effects of the water (channels in the mud, rain-flattened leaves) would remain. Water itself will probably not remain, but even if it does, it wouldn't be nourishing.