Rain

The Rain is a timed environmental hazard deadly to the player and all other creatures. It appears at the end of every cycle once the in-game timer has run out. It is preceded first by a darkening of the screen and then by rumbling and screen-shake. These effects increase in intensity as the first drops of rain appear. The rain quickly increases in intensity until it is lethal, either crushing or drowning all creatures in affected rooms.

To avoid this hazard, the player must seek shelter.

Variation of Rain
The arrival of the Rain has different effects depending on the room. In most outdoor rooms, the Rain directly impacts the player's movement, most severely in areas with no overhead cover. The Rain kills the player faster depending on its strength. In most indoor rooms, the Rain causes flooding which can drown the player. In particular areas such as Five Pebbles, the upper limits of The Wall, Sky Islands's Communications Array, the lowest subregion of Subterranean (Depths) and any shelter, the Rain does not appear.

In The Leg and The Underhang, the green sparks floating around the area accelerate and bounce around at high velocity, typically stunning and then killing the player in a matter of seconds.

Both The Wall and Communications Array feature rooms where the rain is permanently non-lethal, as a transition between higher, safe rooms and lower, lethal rooms.

In the minute before the end of a cycle in areas where Rain occurs, the background darkens. At thirty seconds before the end of a cycle, vibrations of the oncoming Rain can be felt and heard. From here, the Rain most commonly increases steadily in strength from a drizzle to a lethal downpour over 45 seconds, after the last pip.

There is also a chance for the Rain and associated vibrations to suddenly stop mid buildup, before becoming lethal. This lasts for roughly 10 seconds with increasing numbers of single heavy droplets marking the end of the intermission. After this the Rain immediately jumps to its full strength and most indoor rooms begin flooding.

Cycles
Each cycle in Rain World has a random duration, visible in the bottom left corner surrounding the karma symbol. The "pips" each represent 30 seconds, and each cycle can last a maximum of 26 pips (13 minutes) with an extra 20 seconds not shown in the timer. The minimum cycle length depends on the selected difficulty - and   have a minimum cycle length of 13 pips (6 minutes and 30 seconds), while   has a higher minimum cycle length of 18 pips (9 minutes). Of all the Slugcats, the has the shortest minimum cycle length of just five pips (2 minutes and 30 seconds). The cycle timer can be seen at any time by viewing the map, and it flashes up automatically once half the cycle is gone.

Pre-Cycles
Pre-Cycles are an event that has a small chance to occur at the start of a new Cycle, at a 2% chance for most Slugcats, in which there is a residual downpour of rain, although not to a degree as severe as normal and with more oscillation, and one that eventually dissipates with time, rather than building up to a climax. During a pre-cycle, most regions and rooms have special spawns, mainly including aquatic Creatures like s, s,, and more rarely s and. This Rain only remains potentially deadly within the first few minutes of the cycle, and will usually have to be waited out as wavering downpours and bullet rain will strike open areas, and rooms that can be flooded start out fully flooded and only gradually drain once the rain calms down, which often leads to the player encountering Creatures that actively die to the rain or have drowned within a once flooded room. The most beneficial aspect of a Pre-Cycle is the total length of the Cycle, which will often be higher than normal and will only start counting down once the rain has fully stopped, as it would appear within a normal Cycle.

During a Pre-Cycle, rain violently pours down on the region, similarly to how it does at the end of a cycle. This rain is less lethal and does not kill the player outright if they are standing out in the open. Instead, the rain bears down on any creature or item not under the cover of terrain or structures, slamming them against the ground until it lets up. It can cause death by knocking Slugcat into death pits, and because of how strong it forces Slugcat down, they can die via fall damage from shorter heights than usual. If Slugcat is in an area with deep bodies of water, the rain forces them under the surface and may cause them to drown.

The rain periodically slows down, allowing for movement in uncovered areas. An optional mechanic, pre-cycle flooding, may also be present if enabled. This causes certain indoor areas to be completely submerged in water, requiring the player to either find another route, attempt to swim through it, or wait the rain out and for the rooms to gradually drain.

Each region in which Shelter Failures are possible has a set of 'Pre Cycle' spawns that replace normal creatures. This includes creatures that can only be encountered via the lineage system such as s while playing as.

The cycle timer is paused during this event, and does not start until the rain completely lets up and the color palette shifts to normal.

This event can occur for any Slugcat except the Saint. It is significantly more common for the Rivulet, and occurs every Cycle for ???.

Shelter Failures
Shelter Failures are a subfeature of the Pre-Cycle Mechanic, where in addition to the unique Creature spawns, increased Cycle length, and the downpour of rain and room flooding, there is a small chance that the shelter that the player has hibernated within is already open and partially flooded at the start of a cycle, in which the shelter cannot be used again until the Slugcat has successfully hibernated within another still functional shelter. Regardless of where the shelter is, it is unavailable to be slept in until the following cycle.

Tips

 * Because the cycle timer is paused during a Pre-Cycle, the player can simply wait it out without risking dying to restricted time. However, shelter failures are relatively long, and if the player dies at any point, they have to wait again.
 * It may, however, be advantageous to do this in areas such as . Because rain is absent from these areas, instead being replaced by electrical storms, the player is at risk of dying instantly upon exiting the Shelter and at any point they are outside.
 * Creatures often attempt to retreat to their dens as the rain ramps up, even if where they are is sheltered; this can be utilized to pass certain areas safely.
 * Unless the player is confident in their handling of underwater controls and mechanics, it is best to avoid flooded areas or turn the option off entirely.

Day / Night Cycle
Within the uppermost rooms of The Wall, in most areas of, and for the entire Region of , deadly rain does not take effect as in other high altitude areas. Instead, day transitions into night, changing the threat music and causing new creatures to spawn. The darkness brought on by the night cycle is intense, so carrying around a light source or utilizing the glow of a is recommended.

The Saint
During Saint's campaign, the normal cycle of the Rain is instead supplemented with the Blizzard mechanic, in which the Slugcat has to maintain their body temperature to combat the increasing snowfall and wind. There is no cycle timer or hard limit on survivable time, and instead there is a variable amount of time before the blizzard starts and eventually increases in its severity, resulting in rapid heat loss with exposure. The smaller gray pips under the player's Karma and food bar indicate their body heat, where at max the Saint will be fully green, and as this decreases the Slugcat slowly becomes more white and starts shivering. When all of the pips appear empty, the Slugcat turns from a now pale blue into a sickly brown, losing motor function and occasionally losing consciousness, until they eventually can no longer move and freeze to death. The player has to utilize heat sources like s and Scavenger Lamp Poles to gain back body heat, and can further maintain this heat by reducing direct contact with snowfall, staying within naturally warmer environments, and even utilizing steam and the heat produced by traveling through Karma Gates. Contact with bodies of water further increase the rate and amount of heat loss, and with regions like Sky Islands and Shoreline, the periods of calm are naturally short and require quick traversal through large exposed areas and those filled with freezing water.

Tips

 * Bubble Weed can be used to prolong breath underwater while searching for shelter in flooded underground rooms.
 * Cycle time does not pass while passing through gates, unless the rain cycle has already started.
 * Cycle time also does not pass during a Shelter Failure, and only starts to pass once the rain stops.