Andrew Plotkin's first serious game, as he terms it, is an intriguing effort: it introduced the IF community to many key Zarfian elements, notably the "cruelty" of making nearly every move vital and closing off the game without warning, and the magic realism that dominated So Far, though it's present here in a much subtler form. Beyond that, though, Change in the Weather offers a remarkably vivid setting, and effectively uses small changes in the landscape to advance the plot.

The story, at first glance, is not overly complicated: you wander away from your companions in a park and get stuck out in the rain on a steep hillside, and must use what comes to hand to keep a bridge from washing out. Watching all the while is a fox who seems to understand the action better than you do; the fox is only relevant on two occasions, but having it around gives you a sense of collaboration in your efforts to save the bridge. At any rate, the story is essentially divided into two; there is a languid opening section that affords a chance to explore the hill, and a breathless second half where you have, by my count, precisely one move to waste (out of perhaps 45 in all). The landscape changes to reflect the onset of the darkness and the rain, but various events--lightning striking a tree, for example--also cause important changes. Virtually every detail is vital; the player is advised to take time in the beginning to observe everything available.

Change in the Weather is a veritable textbook for authors who want to know how to create and then change a mood, or infuse a scene with tension. The changes in the landscape, while important to the plot, are perhaps even more important for the atmosphere they create. In the first part, for example, we get this: 

You're standing on a ledge, on a rather steep, overgrown hillface. Greenery
hides the stream below and the hilltop above, and the meadows and sky beyond
sweep away into the incandescent west.
Whereas, after nightfall: 
You're standing on a ledge, on a rather steep, overgrown hillface. Rain hides
the stream below and the hilltop above, and to the west is only dark.
The changes in the setting to induce a change in mood recall Wishbringer, and while Change in the Weather owes less to fantasy than Wishbringer, the details evoke a similar sense of unease, reinforced by voices in the distance which seem to be calling your name, and which become louder as you dash around the hillside. Plotkin is particularly skillful in using timed events and small details to heighten the tension: once the protagonist awakens amid the storm, everything appears to be happening at once--runoff starts flowing, lightning strikes a tree and a branch falls, the stream rises, and the voices in the distance persist at the edge of the player's consciousness. The various events are all separated by line breaks, so they have the feeling of independent events that are following their own paths. Plotkin uses sound as well as visual details to build the tension: a bush gives way with a "small snap," the tree falls with a "splintering crash" after the "Crack!" of thunder--and the dizzy rush of detail among all the concurrent events produces a whirling, desperate confusion. Though we get little of the protagonist's thoughts, it seems plausible to support that he or she is somewhat less than calm, and the author does his utmost to transfer the growing sense of panic to the player. When lightning dazzles you and leaves you in the dark again, you "blink furiously, trying to sort out the shadows from what's really there." That connotes both the sensory struggle--night vision shattered in a flash of light--but also the urgency; your task is sufficiently pressing that you try to blink away the afterimages and keep moving, lest you waste valuable time. For the most part, Plotkin is content to show the details rather than telling the player how to feel, and the few exceptions--digging a trench, you "claw desperately" at the earth--are well placed.

The author notes that this is a "cruel" game, and he doesn't exaggerate: it is virtually impossible to solve it on the first try, or even on the first ten tries. Making every move count is one form of cruelty, and the writing is good enough (and the mood sufficiently pervasive) that the game doesn't get dull even after many repetitions. Another form of cruelty--a required action in the first half of the game which is much less than obvious, and which is clued rather subtly--is less successful, to my mind, because it weakens the game's logic: it's one thing to have to make sense of a wide variety of concurrent events, it's another to make an intuivie leap that a key object is hidden in a strange place. The sense in the second half, even when I failed to think of something vital on the proper move, was that, well, if I'd been really thinking, I would have known that. And other elements, the "magic realism" feel--the fox's remarkable prescience, a certain change that the rain couldn't logically cause--don't break the logic, somehow, because they seem only just outside the realm of usual possibilities; they seem like the sort of things we feel could happen easily enough, given a minor incursion of the supernatural. It's hardly less logical that the interlocking parts of the game come together in the way they do, after all, but the player isn't about to question that; likewise, the magical bits require only the sorts of suspension of disbelief that a player is happy to make anyway. Moreover, certain bits of the game that can't quite be put down to magic remain speculative at the end, perhaps intentionally so; a Zarf game wouldn't be a Zarf game if everything were fully explained (or even explainable).

The charm of Change in the Weather, for me at least, lies in the way it infuses a relatively ordinary setting with such a range of feelings: from pleasant sunset to violent, ominous night storm to placid dawn, the same locations are rewritten to instill different moods. Like all good writers, Plotkin is sparing with the adjectives and more often uses verbs to produce the desired effect: 

You are high on the hill; it rolls downward and off to the west. Beyond the
trees and brush, meadows glow in the thickening sunlight. Behind you stands the
last stony lump of hill. A narrow trail curves away to the northwest.
The various elements of the scene are given personality by "rolling" and "glowing" and such, and the impression of a peaceful sunlit scene is clear enough that more description isn't necessary. Likewise, after sundown: 
A wide angular tongue juts out from the hillside. A black expanse stretches to
the north and west, impenetrable with rain. Every few moments, a directionless
flicker of lightning tries to pull detail from the darkness; but there is only
mist.
Again, elements of the scenery get active verbs rather than simply being described, and the adjectives are placed to convey something essential rather than simply piling on the description: the "directionless" lightning illustrates how the flash comes from and leads nowhere in particular, the "impenetrable" darkness limits the immediate range of vision. The best atmospheric effects are those that aren't obviously trying to be, and in that respect, Change in the Weather succeeds--and, as in Wishbringer, only minor changes are necessary to convey the developments in the landscape.

Though its scope is more limited than that of So Far, Change in the Weather is accomplished in its own right. Even if "cruel", it's successful both as a puzzle-solving challenge and as an evocative setting.