Weather
Those who are adventuring in the wilderness must always keep an eye to the sky. Not only to look out for dragons, but also for the weather, which can be just as lethal as any foe if it turns against you.
Weather Parameters
The weather is decided by temperature, precipitation and wind. These parameters range from 1 to 10 and each start at 5 (or d10/3d4-2).
Each day, roll a d6 for each parameter and apply the following table. If the party travels very quickly, as by teleporting, determine new base values for their new location, either by rolling or DM fiat.
| d6 | Effect |
|---|---|
| 1 | -2 |
| 2-3 | -1 |
| 4-5 | +1 |
| 6 | +2 |
Biomes and Seasons
Different biomes and seasons provide flat modifiers to the values.
| (temp/prec/wind) | Polar | Boreal | Temperate | Tropical |
|---|---|---|---|---|
| Arid | Arctic Desert -6/-4/+2 | Dry Tundra -3/-3/+2 | Arid Steppe +1/-2/+1 | Sandy Desert +6/-4/+2 |
| Plains | Frozen Tundra -5/-2/+3 | Moorland -2/+1/+2 | Brush Prairie 0/+1/+1 | Savannah +4/+1/+2 |
| Forest | Arctic Forest -4/+1/-1 | Taiga -2/+2/-1 | Deciduous Forest +1/+3/-2 | Rainforest +4/+4/-3 |
| Alpine | Arctic Mountains -5/+2/+3 | Boreal Mountains -3/+2/+3 | Temperate Mountains 0/+2/+3 | Tropical Mountains +2/+2/+2 |
| Ocean | Arctic Ocean -4/-1/+2 | Northern Ocean -2/0/+2 | Temperate Ocean +1/+2/+2 | Tropical Ocean +4/+3/+1 |
| Season | Temperature | Precipitation | Wind |
|---|---|---|---|
| Early Spring | -1 | 0 | +1 |
| Late Spring | 0 | +1 | 0 |
| Early Summer | +1 | 0 | -1 |
| Late Summer | +2 | -1 | 0 |
| Early Autumn | +1 | +1 | +1 |
| Late Autumn | 0 | +2 | +2 |
| Early Winter | -1 | 0 | 0 |
| Late Winter | -2 | 0 | +1 |
The Weather Tables
In general, any adverse conditions remain for higher levels on the tables. Ie, the effects of light rain are also present in heavy rain.
| Temperature | Condition | Effect |
|---|---|---|
| 1-2 | Freezing | Exposure |
| 3-4 | Chilly | If wind > 7, Exposure |
| 5-6 | Normal | |
| 7-8 | Warm | If precipitation < 2, Exposure |
| 9-10 | Hot | Exposure |
Exposure: Travelers in these conditions must make DC 14 Constitution saving throws at the end of each day of travel or suffer a level of Exhaustion the next morning. This can be alleviated by proper equipment (special clothing/tents/magical gear) or certain racial traits. In warm weather, fire resistance negates exposure from temperature, and in cold weather the same is true for cold resistance.
In the harshest conditions, these protections might only give advantage on the save, or prevent an auto-failure. Unprotected creatures could also need to make more than one save per day, perhaps as many as one per hour spent travelling unprotected.
| Precipitation | Condition | Effect |
|---|---|---|
| 1-2 | Arid | Foraging is harder, especially for water. Disadvantage on Survival checks to forage. |
| 3-4 | Clear sky | |
| 5-6 | Cloudy | |
| 7-8 | Light rain | Disadvantage on Survival checks made to follow tracks. |
| 9-10 | Heavy rain | Exposure. All Perception checks are made with disadvantage. |
If temperature is below 2, precipitation falls as snow instead of rain.
| Wind | Condition | Effect |
|---|---|---|
| 1-2 | Becalmed | Sailing ship travel speed is halved. |
| 3-4 | Light | |
| 5-6 | Moderate | |
| 7-8 | Heavy | Ship travel is difficult. Ranged weapons only work up to their short range. |
| 9-10 | Storm | Exposure. Flying speeds are halved. All travel is difficult. All ranged weapons have disadvantage. |
| d8 | Wind From |
|---|---|
| 1 | North |
| 2 | Northeast |
| 3 | East |
| 4 | Southeast |
| 5 | South |
| 6 | Southwest |
| 7 | West |
| 8 | Northwest |
Ship travel speed is halved in the direction of the wind. With heavy winds, even travel by foot might be impeded in the direction of the wind.
| 2d6 | Wind direction change |
|---|---|
| 2 | -3 |
| 3 | -2 |
| 4-5 | -1 |
| 6-8 | 0 |
| 9-10 | +1 |
| 11 | +2 |
| 12 | +3 |
Roll on this table every day as with the other values. Unlike the other ones, wind direction loops around.
Special weather conditions
- 9+/9+/9+, monsoon
- -2/9+/9+, snowstorm
- 7+/7+/x, roll a d6 for lightning intensity: 1-3 none, 4 some, 5 moderate, 6 heavy.
Magical influences
Certain spells can influence the weather. Some just affect a small area, others might affect a whole region. Most local spells work as usual, such as Control Winds. The major exception is the Control Weather spell. If cast, it instead modifies the base rolls by 1, in either direction. These changes persist after the spell fades, and affect the whole region.
The Storm Sorcerer's Storm Guide feature also work as normal. Both the Tempest Cleric and Storm Sorcerer's flying speeds are unaffected by high winds.
Predicting the Weather
To attempt to predict the weather, a player can make a DC 16 Nature check. If successful, they learn how much and which direction one of the parameters will move tomorrow (roll tomorrows deltas when this happens). This can either be temperature, precipitation, wind speed or wind direction. On a failure, no information is learned.
If you try to learn multiple parameters, a separate roll is made for each. If any prediction check is successful, further checks are made at disadvantage.
Example
Travel through an early autumn (+1/+1/+1) boreal forest(-1/+2/-1) for two days, then across a boreal mountain (-2/+2/+3) for three days, before entering an arctic plains (-4/-2/+3) for two days
Early autumn boreal forest mod = 0/+3/0
Early autumn boreal mountain mod = -1/+3/+4
Early autumn arctic plains mod = -3/-1/+4
Initial rolls are 1/10/5e (temp/prec/wind & wind direction)
- Day 1: 1/10/5 modded to 1/10/5e, heavy snow and freezing temperatures. Wind is not too bad, from the east.
- Day 2: 2/9/6 modded to 2/10/5n , the heavy snows continue. Roads have become useless, as everything is covered in about two feet of snow.
- Day 3: 3/8/4 modded to 2/10/8n, the snowfall continues unabated, but the wind picks up as you gain altitude, swirling the snow around.
- Day 4: 1/7/3 modded to 1/10/7w, same hard weather as yesterday, although the winds are no longer straight in your face
- Day 5: 1/6/2 modded to 1/9/6n, the snow shows no sign of stopping, but the mountains give way to the northern tundra
- Day 6: 3/4/3 modded to 1/3/7e, the mountain seems to provide some shelter from the snow, as the icy blue sky greets you in the morning
- Day 7: 2/2/2 modded to 1/1/6e, a crystal clear sky with biting cold. A vast expanse of cold.