Improved Temperature and Weather Rules – DnD 5e – RPGBOT

Introduction

5e’s temperature/weather rules are insane. And not in a good way.

On any given day, there’s a 15% chance that the temperature will be too cold by 1d4*10 degrees. That means that on a day which might normally be 70 degrees fahrenheit (perfectly comfortable weather), there’s a non-zero chance that it will suddenly be 30 degrees (slightly below freezing). Even crazier, there’s a 15% chance to go the other direction and these probabilities are not related in any way, so the temperature could whip from 30 degrees one day to 110 the next. The rules suggest adjusting for terrain and season, but I don’t know of anywhere on earth with temperature swings that wide.

Similarly inexplicable, the rules for cold and hot weather work differently: cold weather doesn’t matter until you get below 0º Fahrenheit (remember that water freezes at 32º), but hot weather becomes a problem at 100º. Heat also becomes increasingly difficult to endure over time, while cold somehow doesn’t. The fact that these two extremes use different rules is difficult to justify.

This article presents alternative rules for temperature and weather. They are assembled from a combination of 5e’s rules, Pathfinder 2e’s rules, actual weather information from the US National Weather Service, and one random XKCD reference. The intent is to make this system feel more accurate and more interesting without making it significantly more complex than the base rules.

This is not a perfectly simulationist solution to weather, nor is it a perfectly realistic interpretation of how one should handle real-world temperature extremes. Please do not read this article and then harm yourself by subjecting yourself to real-world temperature extremes.

Table of Contents

• Introduction
• Temperature and Weather
  • But it feels like…
  • Equipment and Precautions
  • Humidity
  • Precipitation
  • Resistances and Immunities
  • Wind
• Putting it All Together

Temperature and Weather

The below temperature ranges are intentionally somewhat “fuzzy”; do not scrutinize the actual temperatures listed in too much detail. DnD characters typically don’t carry thermometers around. The temperatures are listed to give you, the DM, a rough estimate of what temperatures fall into what ranges and what effects you should apply in each of these “temperature bands”.

These rules also aren’t intended to apply to creatures native to the local climate. With rare exceptions, creatures native to any locale are adapted to the local weather. Mammals grow thick pelts to survive cold winters, etc.

Category	Temperature	Description	Effect
Incredibly Cold	-80º F or colder (-62º C or colder)	Lethally cold without precautions.	DC 10* Constitution saving throw every 5 minutes or gain one level of exhaustion.
Extremely Cold	-79º F to -21º F (-61º C to -29º C)	Spit goes “clink”.	DC 10* Constitution saving throw every 10 minutes or gain one level of exhaustion.
Severely Cold	-20º F to 0º F (-28º C to -18º C)	Frostbite likely without precautions.	DC 10* Constitution saving throw every 30 minutes or gain one level of exhaustion.
Cold	0º F to 32º F (-17º C to 0º C)	Water freezes.Frostbite possible. Warm clothing required for prolonged periods.	DC 10* Constitution saving throw at the end of each hour or gain one level of exhaustion.
Mildly Cold	33º F to 60º F (1º C to 15º C)	Typically comfortable in warm clothing.	None.
Comfortable	60º F to 79º F (16º C to 26º C)		None.
Mildly Hot	80º F to 90º F (27º C to 32º C)	Typically comfortable in light clothing.	None.
Hot	90º F to 104º F (33º C to 40º C)	Light clothing required for prolonged periods.	DC 10* Constitution saving throw at the end of each hour or gain one level of exhaustion.
Severely Hot	104º F to 125º F (41º C to 51º C)	Heat exhaustion likely, and heat stroke possible with prolonged exposure and/or physical activity	DC 10* Constitution saving throw every 30 minutes or gain one level of exhaustion. Creatures must consume twice as much water as normal or they make this save with Disadvantage.
Extremely Hot	126º F to 139º F (52º C to 59º C)	Heat stroke is highly likely.	DC 10* Constitution saving throw every 10 minutes or gain one level of exhaustion. Creatures must consume twice as much water as normal or they make this save with Disadvantage.
Incredibly Hot	140º F or warmer (60º C or warmer)	Lethally hot without precautions.	DC 10* Constitution saving throw every 5 minutes or gain one level of exhaustion. Creatures must consume twice as much water as normal or they make this save with Disadvantage.

* – increase DC by 5 each time the creature rolles the save. Reduce the DC by 5 for every hour the player spends recovering in comfortable temperatures.

But it feels like…

Weather doesn’t always “feel” like the actual temperature. Conditions like humidity, what you’re wearing, and sun exposure can all affect how your body responds to temperature. A breeze can make a hot day more comfortable, but it can also cut right through your clothing on a cold winter day. Creatures may also have resistance or immunity to cold or fire damage, providing extraordinary protections not available to real-world humans.

Equipment and Precautions

Creatures that are well equipped to handle the temperature or who take precautions to protect themselves can often mitigate extreme temperatures.

Clothing is humanoids’ first line of defense against the elements. Wearing warm clothing in the winter and cool clothing in the summer For creatures wearing multiple types of clothing (such as cold weather gear over heavy armor), use whichever type of clothing is the warmest. For example: If a creature is wearing heavy armor and hot weather clothing, use the modifier for heavy armor.

• Cold weather clothing: Clothing including heavy gloves, insulated boots, thick jackets, fur-lined cloaks, etc.
  • Move two steps toward hot temperatures
• Heavy armor: Full plate and similar heavy armor includes layers of chain mail and padded clothing, all of which can insulate the wearer.
  • Move one step toward hot temperatures
• Heavy clothing: Cloaks, long clothing, multiple layers, etc.
  • Move one step toward hot temperatures
• Light clothing or no clothing: Short sleeves, etc. Keep in mind that going unclothed or with lots of bare skin in hot temperatures can actually make things worse due to sun exposure. Please don’t read this article and die of heat stroke.
  • Move one step toward cold temperatures
• Hot weather clothing: Long clothing made of breathable materials, head coverings, and other garments build to protect from the sun while still remaining breathable. Clothing wetted with cool liquid can also suffice, so long as the garment is wetted repeatedly.
  • Move two steps toward cold temperatures

In addition to wearing clothing, other precautions can impact temperature extremes.

• Cool apparatus: Any mechanism used to cool the user. A device blowing cool mist, a creature fanning another creature, etc.
  • Move one or more steps toward cold temperatures
• Cooling food and drink: Iced beverages, frozen foods, and potentially spicy foods like peppers (they make you sweat without raising your body temperature) can make hot weather more tolerable.
  • In hot weather, advantage on your next save against hot temperatures. In cold weather, disadvantage on your next save against cold temperatures.
• Direct sun exposure: Sun exposure can make temperatures feel warmer. In some cases, other sources of light can have similar effects.
  • If exposed to the sun for the vast majority of any given time period, move one step toward hot temperatures
• Natural Adaptations: Some creatures are native to extreme climates, but might not have actual damage resistance. Those creatures can more readily handle cold or hot temperatures than creatures not similarly adapted. This might include creatures with specific physical adaptations, but at the DM’s discretion it might also include creatures who have spent a significant amount of time adapting to that climate.
  • At the DM’s discretion, the creature treats all temperatures as one step colder or one step hotter depending on their adaptations.
  • At the DM’s discretion, the creature might ignore the effects of humidity.
  • At the DM’s discretion, the creature might ignore the effects of direct sun exposure.
• Shade: Taking frequent breaks to cool off in the shade can make hot temperatures much more manageable. This might mean sitting under a shady tree, or it might mean traveling in a litter with a shade over you.
  • If the vast majority of a given time period is spent in the shade, mobe one step toward cold temperatures
• Warming apparatus: Any mechanism used to warm the user. A hot stone which radiates heat, a camp fire, etc.
  • Move one or more steps toward hot temperatures
• Warming food and drink: Consuming warm food and beverages like tea or hot soup can make cold temperatures feel more comfortable. However, these benefits aren’t as consistent as other countermeasures.
  • In cold weather, advantage on your next save against cold temperatures. In hot weather, disadvantage on your next save against hot temperatures.

Humidity

Humidity makes temperatures feel more extreme. In cold temperatures, the cold clings to you. In hot temperatures, the humidity makes it hard to catch your breath, and despite sweating it can be difficult to cool yourself, much like standing in a sauna.

• Low Humidity: Air is dry or not significantly humid.
  • No effect.
• Moderate Humidity: Air is somewhat humid.
  • Move one step away from comfortable.
• High Humidity: Air is steamy, foggy, or there is otherwise a lot of water hanging in the air.
  • Move two steps away from comfortable.

Precipitation

Rain, snow, sleet, or other forms of precipitation can both lower the actual temperature and make the current temperature feel cooler. However, it can also leave the air humid when the precipitation stops.

• Light Precipitation: Light rain, gentle snowfall, or similar conditions.
  • Move one step toward cold temperatures.
  • Disadvantage on Wisdom (Perception) checks to see at long distances.
• Heavy Precipitation: Heavy rain, snow, or similar conditions.
  • Move two steps toward cold temperatures.
  • Everything in the are of precipitations is lightly obscured
  • Creatures in the area have Disadvantage on Wisdom (Perception) checks that rely on sight. Heavy rain or hail also imposes Disadvantage on Wisdom (Perception) checks and immediately extinguishes open flames, such as campfires and torches.

Resistances and Immunities

Resistances or immunities, whether natural or conveyed by magic, can protect creatures from temperature extremes just as they protect creatures from damage.

• Cold Immunity: No negative effects from anything below comfortable temperatures.
• Cold resistance: Treat cold temperatures as 3 steps closer to comfortable.
• Fire resistance: Treat hot temperatures as 3 steps closer to comfortable.
• Fire Immunity: No negative effects from anything above comfortable temperatures.

Wind

Wind can make temperatures feel much colder. The National Weather Service’s Windchilld Chart shows combinations of temperature and wind speed and how quickly frostbite sets in under those conditions. On a hot day, wind can feel welcome. On a cold day, it makes the cold that much worse.

• Moderate Wind:
  • Move one step toward cold temperatures
• Strong Wind:
  • Move two steps toward cold temperatures
  • Disadvantage on ranged weapon attack rolls and Wisdom (Perception) checks that rely on hearing
  • Extinguishes most open flames, disperses fog
  • Flying by non-magical means is impossible. Most flying creatures must land by the end of their turn or fall.
  • Depending on terrain, may also cause sand, snow, or dust to obscure vision, imposing Disadvantage on Wisdom (Perception) checks to see

Putting it All Together

That was a lot. It feels like a lot to keep track of when it’s all listed out like it is above, but when you think about handling temperatures in real life it should all feel intuitive. Let’s look at some examples.

Susan, a human, is visiting her friend Snek, the lizardfolk, at home in the local swamp. The swamp is moderately humid today, and it’s a hot summer day (the “Hot” temperature band). Susan often travels in heavy armor, but due to the weather she instead wears light clothing. Even so, it’s still very hot, so Susan drinks plenty of water and takes frequent breaks to rest in the shade.

How does that all total up? We start from the “Hot” weather band. We go one step away from Comfortable due the humidity (toward hot temperatures in this case), then one step toward cold temperatures due to Susan’s light clothing. That still puts Susan in the Hot weather band, so she’s going to make Constitution saves unless she takes additional measures. She remembers to drink plenty of water, so she won’t suffer Disadvantage in any saves she makes, but she also takes breaks in the shade to cool off, reducing the effective temperature from Hot to Mildly Hot, which is uncomfortable but not problematic. Susan tells herself that she’ll buy some hot weather gear next time she plans a visit.

So how does Snek handle the situation? Snek grew up in the swamp, and lizardfolk, much like regular lizards, are cold blooded and enjoy direct sunlight. That gives Snek several natural adaptations which the DM rules will mitigate the weather. The DM decides that Snek is accustomed to mild humidity, warm temperatures, and direct sunlight, so the DM will ignore the humidity, move Snek’s effective temperature band one step toward cold due to their comfort in warm temperatures, and ignore the detriments of direct sunlight. So on a Hot day, Snek experiences it as “Mildly Hot”. Snek decides to go without clothing (typical for lizardfolk), reducing the temperature band one step further to “Comfortable”. Snek is right at home.

Susan and Snek are later dragged into a Rime of the Frostmaiden campaign and are exposed to a great deal of cold weather. They find themselves in the middle of a blizzard on what was already a Severely Cold day. Icewind Dale is trapped under perpetual winter, so the limited sunlight isn’t helping. The DM rules that the wind is mild but the precipitation is heavy. Susan and Snek came prepared and they’re wearing cold weather clothing.

Starting from the Severely Cold band, we adjust downward two bands for heavy precipitation, and one more band for mild wind, putting the weather below Incredibly Cold by one step. Susan and Snek are both wearing cold weather clothing, which raises their effective temperature by two steps back to Extremely Cold. They’re in a lot of trouble!

They won’t be able to light a fire, and there’s no cover nearby, so they both drink potions of cold resistance. Cold resistance raises their effective temperature two more steps to Mildly Cold. The DM then applies Snek’s adaptation to warm climates, which drops Snek back down to Cold. Snek, seeing that Ten Towns is exactly as bad as they were told, pulls out a thermos of warm soup (warming food and drink) and hopes for the best as he prepares for a series of Constitution saving throws unless the snow lets up or they find a place to take cover from the storm.