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Weather Events

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Every day of travel, roll a d20. On a 20, the adventurers come across one of the following weather events.

Table: Weather Events
d6 Weather Event
1 Dust Devil
2 Fog
3 Gusting Zephyrs
4 Storm
5 Tremor

Dust Devil

A whirlwind of dust randomly moves across the region. A 5d10-foot × 5d10-foot area defines the dust cloud, and it moves 1d6 × 5 feet in a random direction each round. A creature caught outside of shelter and in the cloud must make a DC 15 Constitution saving throw at the end of its turn or be blinded for 1 round. Failure on this save by 5 or more causes a creature to take 1d4 slashing damage.

Fog

A massive bank of mist roils over the landscape and doesn’t dissipate for 1d4 hours. The heavy fog blocks even darkvision, making all creatures and objects within it heavily obscured.

Gusting Zephyrs

Strong winds suddenly fill the atmosphere. The force of the gust automatically extinguishes candles, torches, and similar unprotected flames. It causes protected flames, such as those of lanterns, to dance wildly and has a 50% chance to extinguish those lights. Ranged attack rolls are made with disadvantage and creatures with a flying speed move at half speed. In addition to the effects noted, these gusts of wind can do anything that sudden blasts of wind would be expected to do— create stinging sprays of sand or dust, overturn delicate awnings or hangings, or keel over a small boat.

Storm

It begins to rain or sleet heavily (depending on the environment). The weather lightly obscures vision and all creatures in the region have disadvantage on sight-based Wisdom (Perception) checks; if the weather is rain, this also applies to hearing-based checks. The weather extinguishes open flames. In the case of sleet, the ground becomes slippery until 1d4 hours after the storm passes, requiring all creatures to succeed on a DC 10 Dexterity (Acrobatics) check to avoid falling prone the first time they attempt to move on it.

Tremor

Earth tremors force all creatures on the ground to make a DC 15 Dexterity saving throw or fall prone. There may be major structural failures nearby, impacting trees and structures within 100 feet. Trees up to 30-foot in height fall in random directions, affecting 5-foot-wide, 30-foot-long areas. Structures collapse into a 15-foot-wide radius bury zone. A creature under the falling items takes 22 (4d10) bludgeoning damage (or half that with a DC 15 Dexterity save). The area underneath the collapsed section then becomes filled with rubble, and is treated as difficult terrain.

Plague of Vermin

A plague of vermin wreck havoc on everything in their path. A Gargantuan swarm of insects, rats, or other appropriate vermin (400 hit points) appears in a random location and begins to move randomly across the region 1d6×5 feet in a random direction each round. Rats cause difficult terrain in a 10-foot square; insects or bats cause disadvantage on ranged attacks and Wisdom (Perception) checks in the same area.

High Mountain or Winter Hazards

There are numerous threats posed by cold climates beyond the bitter cold.

Falling Ice

Fierce winds knocked down icicles from above, carrying them down to crash below dealing 2d8 bludgeoning and piercing damage. Creatures that make a DC 14 Dexterity saving throw take half damage. Any creature that takes 5 or more damage from falling ice is knocked from the mountainside, falling 30 feet (taking 3d6 bludgeoning damage upon landing).

Microstorm

Pockets of pressure generate a spontaneous microstorm to whip down the mountain, hitting the adventurers as they are halfway through a stretch of climbing. The remaining distance to be traveled is 150 feet from the lead creature in a gradual horizontal ascent. The first round as sprinklings of water begin to fall, the DC of Strength (Athletics) checks to stay on the wall is 8, or 11 to move at half speed. For every 2 rounds afterward the DC to remain on the wall increases by +1 and the DC to continue moving increases by +2. A microstorm lasts for 3d4+3 rounds.

Sinking Crevasse

While traveling up a hill the creatures’ weight shifts a shelf of ice over an air pocket, breaking it open in a crevice that widens to swallow up everything nearby! The first round a sinking crevasse is activated the creature that triggers it (roll randomly to determine which) makes a DC 18 Dexterity saving throw or falls into the air pocket, dropping 1d4 x 10 feet (taking 1d6 bludgeoning damage upon landing for every 10 feet fallen). Adjacent creatures make this saving throw with advantage. Failing by 5 or more means an adjacent creature also falls, but otherwise they grab onto the edges of the crevice and can climb up on their turn with a DC 13 Strength (Athletics) check. At the end of the round, if any creature is within 10 feet of the sinking crevasse’s edge it expands 5 feet in every direction, widening the hole and dropping clinging creatures inside. A creature in the bottom of a sinking crevasse must dig their way out in a process that takes an hour.

Snow Slide

Sunlight glancing off the top of a snowy incline has shifted it, rolling chunks down the mountain and triggering more tides of white to roil downhill. Creatures able to brace themselves against the terrain (using a boulder or tree) make a DC 15 Strength saving throw and freestanding creatures make a DC 16 Dexterity saving throw. Failure causes a creature to take 3d4 cold and bludgeoning damage and gain the grappled condition as it rolls down the hill with the snow, traveling 60 feet each round until it regains its footing.

Each round a rolling creature makes a DC 12 Dexterity saving throw to stop. After rolling for 2 rounds, each round there is a 50% chance a creature is buried in the snow. A buried creature gains the restrained condition and takes 1d4 cold damage each round until it succeeds a DC 13 Strength (Athletics) check to climb and wriggle out.