Playing with Weather

I doubt this is at all realistic, and it's probalby too fiddly for most people, but here's a draft of a general weather chart that I'm considering using for the campaign.

Table: Random Weather
d20	Weather	Wind Table	Temp Table	Precip Table	Cold Climate	Temperate Climate	Desert
1-13	Normal weather	1d10	1d10	1d6-1	Cold, calm	Normal for season	Hot, calm
14-15	Abnormal weather	2d6	2d6	2d4	Heat wave (01-30) or cold snap (31-100), 1d8+12 on Temperature Table	Heat wave (01-50) or cold snap (51-100) 1d8+12 on Temperature Table	Hot, windy
16-17	Inclement weather	3d4	3d4	1d4+6	Precipitation (snow)	Precipitation (normal for season)	Hot, windy
18-19	Storm	1d10+6	1d10+6	1d6+6	Snowstorm	Thunderstorm, snowstorm	Duststorm
20*	Powerful storm	1d10+10	1d10+10	1d4+8	Blizzard	Windstorm, blizzard, hurricane, tornado	Downpour
* Roll d20 again – if abnormal weather is indicated (14-19), the storm is a powerful storm as listed below, if a second 20 is rolled, the storm is a “storm of the century” table listed below.

Wind Table		Temperature Table***		Precipitation Table****
1	No Wind 0 mph	1	10 degree change	0	Very dry, cloudless
2-3	Light Wind 0-10 mph	2-3	5 degree change	1	Dry, clouds
4-7	Moderate Wind 11-20 mph	4-7	No change	2-3	Dry, very cloudy
8-10	Variable Winds**	8-9	5 degree change	4-5	Partly cloudy, brief drizzle
11-12	High Winds 20-50 mph	10	10 degree change	6	Rain, 2d4 hours, overcast
13-14	Severe Wind 50-70 mph	11-12	15 degree change	7	Heavy Rain, 3d4 hours
15-16	Dangerous Wind 70-90 mph	13-15	20 degree change	8	Soaking Rain, 2d6 hours, overcast
17	Deadly Wind 90-120 mph	16-17	25 degree change	9	Hard Rain, 3d8 hours, thick cloud cover
18	Hurricane Winds 120-150 mph	18	30 degree change	10	Hard Rain, 2d12 hours including 1 hour of hail, sun-blocking clouds
19	Tornado Winds 150-200 mph	19	40 degree change	11	Hard Rain, 6d4 hours, flooding, sun-blocking clouds
20	Unnatural Winds 200+ mph	20	50 degree change	12	Hard rain, 24 hours, flooding, extreme lightning, sun-blocking clouds
** Variable Winds: Winds blowing from 10-40 (1d4x10) mph with gusts 50-90 mph (1d4+4x10). Check for gusts any time something is attempted that might be adversely affected by winds *** Temperature changes are based on the previous day’s temperatures. Unless otherwise directed, a 50% chance of raising and 50% chance of lowering temperatures. **** In temperate climates, use the table as is. In cold climates, consider rain to be snow unless a heatwave is indicated. In desert climates, use cloud cover only unless 20, powerful storm has been rolled on the weather table, then include the rain as well.

Storm of the Century
1d8	Cold Climate*****	Temperate Climate	Desert
1	Temp drop 30 degrees, 6d8 inches of snow lasting 1d4+3 days	Hurricane/Tornado cluster (2d4 tornadoes touch down)3d6+12 inches of rain over 24 hour period, massive flooding	Snow on the Sand – an impossible combination of events occurs, causing 1d4 inches of snow per hour to fall in the region, temperature drops to 30 degrees during the day and -5 degrees at night. Snow falls for 1d4+3 hours and melts at a rate of 1” per hour once the snow stops. Unprotected creatures take 1d4 hp damage per turn.
2-4	Temp drop 30 degrees, 2d12+12 inches of snow lasting 1d6 days	1d8+4 inches of rain falls for 1d12+12 hours, flooding, cluster lightning	Downpour – 1d4+4 inches of rain falls in a 6 hour period causing massive flooding.
5-7	Temp drop 40 degrees, 4d6 inches of snow lasting 1d4 days	Hail the size of grapefruits falls for 10d6 minutes (each does 1d6 damage), +1d4+8 inches of rain over 12 hour period, flooding	Duststorm and rain – 100+ mph winds drive a massive dust storm for 1d4 hours ahead of a huge storm front, which will bring 1d4 inches of rain in 2 hours.
8	Temp drop 40 degrees, 2d6+24 inches of snow lasting 1d6+5 days	Golf ball sized hail for 10d4 minutes (1 point of damage each), +12d6 inches of rain over 20 hour period, cluster lightning	Black Blizzard – dust storm so thick that it blocks out the sun for 2d12 hours, any living creature caught in a Black Blizzard has a 1d10% cumulative chance per hour of dying due to exposure
***** In a cold climate storm of the century, creatures left exposed to the elements will take 1-4hp damage per hour (creatures born/bred in cold climate get a save, half damage if failed, no damage on successful save)