Control Weather: The Magic-User can perform any one of the following weather control operations with this spell: Rain, Stop Rain, Cold Wave, Heat Wave, Tornado, Stop Tornado, Deep Clouds, Clear Sky. [OD&D Vol-1, p. 31]We start with OD&D. Note that Chainmail has no control weather spell -- although it does have some optional rules for random weather [CM, p. 21-22], and the options above are at least semi-compatible with the possibilities there.
Recall that OD&D spells only go up the 6th level, and this is a 6th-level spell, so it is intended to be among the most powerful magics in the game (it's actually the very last magic-user spell in the list, which is organized by some principle other than alphabetization). Notice that there is no range, and no duration specified (indefinite? one battle(field)? DM's choice?). Most of the options would require DM adjudication on the exact in-game effects (e.g., Rain, Cold Wave), although at least one could be clued-in from Chainmail (where it says: "Excess heat... Fatigue doubled, greater chance of fire in dry grass or woods if dry [p. 22]), and perhaps a "Tornado" could be simulated by the Air Elemental "Whirlwind" ability. If the spellcaster has carte blanche to instantly create and control any of these conditions, then it is a very powerful spell, indeed.
Advanced D&D (1st Edition)
Control Weather (Alteration)The text above is copied from the clerical spell roster; the magic-user spell references this (again at 6th level), with half the maximum duration (4-24 hours), and arcane-style material components ("burning incense, and bits of earth and wood mixed in water."). [AD&D 1E PHB, p. 83]
Duration: 4-48 hours
Area of Effect: 4-16 square miles
Components: V, S, M
Casting Time: 1 turn
Saving Throw: None
Explanation/Description: The control weather spell allows a cleric to change the weather in the area he or she is in at the time the spell is cast. The spell will affect the weather for from 4 to 48 hours (4d12) in an area of from 4 to 16 square miles (4d4). It requires 1 turn to cast the spell, and an additional 1 to 4 (d4) turns for the effects of the weather to be felt. The control weather spell will not radically change the temperature, i.e. from below zero to a 100 degree temperature heat wave. The weather control possible depends upon the prevailing conditions:
All three aspects of the weather (clouds/precipitation, temperature, and wind) can be controlled, but only as shown. For example, a day which is clear, warm, and with light wind can be controlled to become hazy, hot, and calm. Contradictions are not possible - fog and strong wind, for example. Multiple control weather spells can be used only in succession. The material components for this spell are the cleric’s religious symbol, incense, and prayer beads or similar prayer objects Obviously, this spell functions only in areas where there are appropriate climatic conditions. [AD&D 1E PHB, p. 52]
So at this point the spell has been fleshed out with range & duration, and they are enormous: on an entirely different scale (days and miles) than almost any other spell in D&D. Other than that, however, a decision has been made to dramatically reign in the power of the spell through a multifaceted series of restrictions. (1) The spell's power has been switched from a blank-check to a "one step adjustment" effect, among several fine-grained categories. For example: You can't just pick "Tornado" at any time now; the natural weather already has to be a "Storm" before you can change it to "Hurricane-Typhoon" (if you wanted such a thing, for argument's sake). (2) There is a very long time-to-effect after casting of 1-4 turns (10-40 minutes by the book in AD&D), which really makes it totally useless in the context of any standard D&D combat. (3) There is the "no contradictions" rule, and also the "only... appropriate climatic conditions" language, which allows the DM to nerf the spell in many ways that it might be used. And finally there is the rule (4) "Multiple control weather spells can be used only in succession", which is to say, "no stacking" (as I read it) -- a key support to #1, that weather will never be altered more than one step from the natural conditions.
The DMG provides its usual errata-like detail:
Control Weather: To find the prevailing conditions at the time the spell is cast, you must know the clime and the season, of course. Sky conditions (cloudy, foggy, partly cloudy, clear), precipitation, wind speed and direction, and temperature must be determined according to the area. Knowing this, you should have no great problem informing the would-be spell caster as to what sort of weather exists. [AD&D 1E DMG, p. 42]
Advanced D&D (2nd Edition)
Control Weather (Alteration)As is most often the case, the 2E spell is just a copy-and-paste of the 1E spell, will some minor reformatting to some of the text. What follows (after the ellipses) is the same table of possible conditions, as seen in 1E. I don't see any changes to the effect of the spell whatsoever.
Duration: 4d6 hrs.
Area of Effect: 4d4 sq. mi.
Components: V, S, M
Casting Time: 1 turn
Saving Throw: None
The control weather spell enables a wizard to change the weather in the local area. The spell affects the weather for 4d6 hours in an area of 4d4 square miles. It requires one turn to cast the spell, and an additional 1d4 turns for the weather conditions to occur. The current weather conditions are decided by the DM, depending on the climate and season. Weather conditions have three components: precipitation, temperature, and wind. The spell can change these conditions according to the following chart.
The upper-cased headings represent the existing weather conditions. The small headings beneath each large heading are the new conditions to which the caster can change the existing conditions. Furthermore, the caster can control the direction of the wind. For example, a day that is clear and warm with moderate wind can be controlled to become hazy, hot, and calm. Contradictions are not possible--fog and strong wind, for example. Multiple control weather spells can be used only in succession.
The material components for this spell are burning incense and bits of earth and wood mixed in water. Obviously, this spell functions only in areas where there are appropriate climatic conditions... [AD&D 2E PHB]
Weather ControlAt this point, as usual, I like to check in on the Aaron Allston Rules Cyclopedia from 1991, which represents the results of divergent evolution of the game along the BXCMI line. The rules above are fundamentally the same as those first laid down in the Expert Rulebook by Dave Cook and Steve Marsh in 1981 (same area, weather categories etc.; although most of the sentence-structures have been rewritten; p. X17). Oddly, the spell does not appear in Frank Mentzer's Expert Rulebook of 1983 (possibly appearing in the Companion rules?) While the earlier Cook text still called it control weather, the name now (in Allston) has for some reason been switched around to weather control (like most of the constituent sentences, actually) .
Range: 0 (magic-user only)
Effect: All weather within 240 yards
This spell allows the magic-user to create one special weather condition in the surrounding area (within a 240 yard radius). The spellcaster may select the weather condition. The spell only works outdoors, and the weather will affect all creatures in the area (including the caster). The effects last as long as the spellcaster concentrates, without moving; if the caster is being moved (for example, aboard a ship), the effect moves also. The spell's effects vary, but the following results are typical:
Rain: -2 penalty to attack rolls applies to all missile fire. After three turns. the ground becomes muddy, reducing movement to half the normal rare.
Snow: Visibility (the distance a creature can see) is reduced to 20’; movement is reduced to half the normal rate. Rivers and streams may freeze over. Mud remains after the snow thaws, for the same movement penalty.
Fog: 20' visibility, half normal movement. Those within the fog might become lost, moving in the wrong direction.
Clear: This cancels bad weather (rain, snow, fog) but not secondary effects (such as mud).
Intense Heat: Movement reduced to half normal. Excess water (from rain. snow. mud transmuted from rock. etc.) dries up.
High Winds: No missile fire or flying is possible. Movement reduced to half normal. At sea, ships sailing with the wind move 50% faster. In the desert. high winds create a sandstorm, for half normal movement and 20' visibility.
Tornado: This creates a whirlwind under the magic-user's control, attacking and moving as if it was a 12 HD air elemental. At sea, treat the tornado as a storm or gale. [RC, p. 54]
So: The BXCMI spell is very different from AD&D's spell. It has a much smaller area: 240 yards instead of some number of square miles (although perhaps that's an academic difference in a standard D&D fight). It lacks the multi-turn "transition" delay, but it does require that the caster be still and concentrate throughout the duration (a restriction that does not appear in AD&D). The suggested effects are actually more reminiscent of the OD&D options, with specific in-game mechanics attached to each, and apparently the caster can switch between any of them instantly and at will (no alternate AD&D "move one step" mechanic). There also isn't any "appropriate climatic conditions" restriction, as was added in AD&D.
Finally, the spell has the cracked-open-door line that says, "The spell's effects vary, but the following results are typical...", implying that the list of effects is not exhaustive, and if the DM/players are so willing, others might be added.
d20 System D&D (3rd Edition)
Control WeatherIn many respects this follows from the AD&D version of control weather. It has the same "10 minute warmup delay" and "no contradictions" language. A similar miles-and-days range & duration are maintained. It's explicit that no concentration is required (as opposed to the BXCMI version).
Level: Air 7, Brd 6, Clr 7, Drd 7, Sor/Wiz 6
Components: V, S
Casting Time: 10 minutes (see text)
Range: Two miles
Area: Two-mile-radius circle, centered on the character (see text)
Duration: 4d12 hours (see text)
Saving Throw: None
Spell Resistance: No
The character changes the weather in the local area. It takes 10 minutes to cast the spell and an additional 10 minutes for the effects to manifest. The current, natural weather conditions are determined by the DM. The character can call forth weather appropriate to the climate and season of the area the character is in.
Season Possible Weather
Spring Tornado, thunderstorm, sleet storm, or hot weather
Summer Torrential rain, heat wave, or hailstorm
Autumn Hot or cold weather, fog, or sleet
Winter Frigid cold, blizzard, or thaw
The character controls the general tendencies of the weather, such as the direction and intensity of the wind. The character cannot control specific applications of the weather. When the character selects a certain weather condition to occur, the weather assumes that condition 10 minutes later (changing gradually). The weather continues as the character left it for the duration, or until the character uses a standard action to designate a new kind of weather (which fully manifests itself 10 minutes later). Contradictory conditions are not possible simultaneously.
Control weather can do away with atmospheric phenomena (naturally occurring or otherwise) as well as create them.
Druids casting this spell double the duration and affect a circle with a three-mile radius. [D&D 3E SRD]
The list of effects, however, has switched backed to a fairly small number of options (in this case, keyed off the current season) which are once again reminiscent of those found in OD&D, with no "move one step" mechanic involved. In some sense, then, this may be looked at as a re-merging of the divergent AD&D and BXCMI lines; it doesn't have any direct mechanical effects listed here, but in many cases those can by synched up with appropriate listings in the 3E DMG.
Edit: At a slightly later date, I realized that the descriptions for the available weather conditions by season were actually taken from the alternate weather spell for AD&D (both 1E and 2E), the druidic weather summoning (6th-level spell). "Thus, in spring a tornado, thunderstorm, cold, sleet storm, or hot weather could be summoned," etc. [AD&D 1E PHB, p. 63]
Control weather is an interesting and imagination-grabbing spell that didn't have a chance to be playtested in Chainmail, first appearing in brief form in OD&D, and requiring significant refinements afterward. The approach to that refinement was very different between the AD&D and BXCMI lines (the former, by Gygax, being notably more liberal with its alterations/revisions; the latter remaining closer to the OD&D source, but with much heavier restrictions to duration, area, and ongoing caster activity).
I had the opportunity to think closely about control weather when I had to deal with its effects in the course of designing my upcoming Book of War D&D-based wargame. Obviously, the spell seemed like a natural fit for inclusion, being a high-level spell with outdoor usage, large area-of-effect, and a natural tie-in to battlefield weather conditions. But it also became obvious that the OD&D effect as written was simply too powerful -- under almost any interpretation, you could instantly summon a heavy storm or "high winds" and shut down all of an opponent's missile troops, for example. The AD&D modification provides a very nice and praiseworthy fix to this situation, I think; giving a "one step adjustment" to natural weather conditions means that it's possible to sway the weather a bit, and the "no stacking" ("only in succession") rule reinforces that there isn't any "cheat" to work around that and completely break the game. That said, control weather will still be an extremely important tactic in your D&D mass combat simulation.
(Illustration by AZRainman under CC2.)