NATURAL WEATHER:
Winds: Winds can range from negligible to hurricane force. They interfere with your ability to move around, disburse gasses, and can even knock you over.
| Wind Force | Wind Speed | Ranged Attacks | STR DC |
| Light | 10 mph | - | |
| Moderate | 20 mph | - | |
| Strong | 30 mph | -2/- | 0 |
| Severe | 50 mph | -4/- | 5 |
| Windstorm | 75 mph | impossible/-2 | 10 |
| Hurricane | 175 mph | impossible/-4 | 15 |
| Tornado | 300 mph | impossible/impossible | 20 |
Ranged Attacks- Penalty for making ranged attacks with physical weapons, including bows, guns, go in the first column. The second number is the penalty for using energy weapons such as blasts or ray guns. Wind generally doesn't affect these but as the speeds increase the battering of the wind against yourself and body makes it difficult to see or aim such weapons.
STR DC: The DC to move through the wind for a medium creature. Get -4 to your check for each size below medium and +4 to each size above medium. Pass the check to move at 1/2 speed against the wind. Fail and you are checked, unable to make forward movement. Fail by 5 or more and you are knocked prone by the force of the wind. Fail by 10 or more and you are blown away by the force of the wind. Flying creatures are automatically treated as if they failed by 1 step further, and must succeed by 5 or more to make any forward progress. Gaseous creatures would automatically fail the save with the worst possible result regardless of size. Incorporeal creatures would not be affected.
The noise of the winds creates a penalty to sound based and smell based perception checks equal to the strength DC.
On top of the strength of the wind, winds of strong or more can cause flying debris. Strong would include papers and other light objects, where tornadoes could include cars or creatures. Every round spend with flying debris would impose a penalty on visual perception checks equal to the strength DC of the wind- which may make perception attacks difficult. It would also cause damage to those caught within- PL equal to the STR DC (half damage with a reflex save at same PL)- nonlethal damage.
Instead of flying debris, there may be a dust or water involved, which makes the same perception penalties, but no direct damage in the winds.
Precipitation
Rain or Snow is interesting as background. Once it becomes severe, it can cause further problems.
Heavy Rain can cause a penalty to all perception checks as it's loud, obscures vision, and washes away scent.
| Precipitation | Perception |
| Light | 0 |
| Moderate | -2 |
| Strong | -4 |
| Severe | -8 |
| Monsoon | -10 |
| Downpour | -15 |
In addition, rain and snow can cause ground effects from floods or snow-cover, and usually accompany winds. Snow usually accompanies low temperature penalties. Freezing rain or ice storms are rain effects with extreme low temperatures and probably cause ice effects on the ground. They can also accompany darkness quite well.
Hail: Hail is another weather event- treat it as a damaging aura, setting the PL based on the severity of the hail, with damage checks ranging to every minute to every round depending on the severity of the hail.
Fog: Fog usually has no wind, and acts simply as a physical obscurement effect for visual. Thick fogs give partial concealment within 5' and full concealment beyond that. If it's a light fog, it probably just imposes a -5 penalty to perception checks and gives partial concealment to people within 30', full beyond that.
Thunder: Random thunder during rain can create a temporary audible obscure effect, and cause sound based powers a chance to fail (if the user must hear himself), probably a 20% fail chance, and sense dependent sound effects to fail altogether. Alternately it could cause a -4 to -20 penalty to audio perception checks depending on severity.
Lightning: Lightning can temporarily light the sky against darkness, but if it strikes a character, treat it as a blast attack- base PL 10, but can be more powerful if you wish, reflex half. A character probably has only a 1 in 20 chance of being targeted by lightning, but a character with lots of metal (or made of metal) might increase these odds to 1 in 10 during severe lightning storms.
Ground Conditions
Cluttered: This could include deep snow, deep leaves, going through garbage, floods, or any other surface that won't support your weight and is about leg-deep. Walking would be at normal speed, but any acrobatic or reflex checks would be at -4. Deeper conditions could impose further penalties and decrease movement speed. Some materials conduct electricity and may make certain attacks more likely to succeed. Vehicles could suffer -4 to -20 or could become stuck in snow, mud, or water and unable to operate at all.
Slippery: Whether it's oil or icy, slippery conditions would force a character to make an acrobatics check if he moves faster than half his speed or fall over. (Vehicles get a -20 to drive checks to avoid losing control- which can be counteracted by driving very slow). Skating is possible to increase speed but uphill travel could be difficult or impossible without special tools.
Earthquake: An earthquake could cause problems even when standing still- or destroy structures around you. GM should assign a PL to the earthquake, anyone touching the ground must reflex save against the PL or fall prone. Buildings and structures anchored to the land must toughness save or take damage, with damaging consequences to creatures near or inside them.
Abnormal Weather
Instead of statting out each- I threw together some abnormal weather conditions you might consider to add flavor to your campaign, travel, or battles.
- Lava Flow
- Overgrown with vegetable matter (vines)
- Raining Fire and Brimstone, or animals (Frogs, Cats and Dogs)
- Sharknado/ Arachnoquake
- Wild Magic / Power Granting / Dead Magic zones or fog
- Gravitational or Magnetic anomalies
- Acidic/Poisonous/Chemical Rains or Fogs
- Meteor Swarm or Raining Debris of some kind.
- Avalanches
- Tsunamis
- Steam Guyser
-Noise Pollution (bull horns, loud music, concerts, etc)
- Columns of Fire (aliens from independence day, earth terraforming, divine retribution)
- Radiation or Nuclear Fallout
-Volcanic Eruption/ Clouds of Ash
Spice up the campaign with a little bit of weather!
