I got the idea during a pickup game in 1982 where I was DMing for some friends. When we could get together I would run modules and such for them, all in Greyhawk. I had just read a Dragon article about weather in the campaign and decided to see how it worked. The adventure was ostensibly a scouting mission through the Vesve to spy on Iuz's border forts. Instead it turned into a survival scenario as an unseasonable blizzard swept the area.
The players loved it, I loved it, and I decided to make a set of charts of my Seaward campaign.
Hope you like them.
Note: The formatting is a little wonky because of Blogger, so please excuse the appearance.
Seaward Weather
First – Check for Unusual Temperatures: Use this chart to determine if a cold snap or heat wave is occurring:
01 Extreme Record Low
02 Severe Record Low
03-04 Record Low
05-96 Normal Temps
97-98 Record High
99 Severe Record high
00 Extreme Record High
'Record High' or 'Record Low' means that the temperatures will be the maximum possible (i.e., if the base temp is 40, avg. high is d10 and avg. low is d20 a 'Record Low' means the high will be 41 and the low will be 20). A 'Severe Record' means use the maximums and add 1d6. An 'Extreme Record' means double the maximums.
Unusual temperatures will last 1-6 days (roll d8-2 with a minimum of 1).
Second – Determine Base Weather: If there are unusual temperatures, follow those rules. Otherwise. roll on the following chart to determine the high and low temperatures, cloud cover, and base chance of precipitation;
|
Month
|
Base Temp
|
Avg. High
|
Avg Low
|
Clear
|
Part Cloudy
|
Cloudy
|
Precip Odds
|
Sunrise
|
Sunset
|
|
Newsun
|
40
|
d10
|
d20
|
01 – 23
|
24 – 50
|
51 – 00
|
46
|
07:11:00 AM
|
05:11:00 PM
|
|
Brightsun
|
42
|
d6+4
|
d10+4
|
01 – 25
|
26 – 50
|
51 – 00
|
40
|
06:45:00 AM
|
05:46:00 PM
|
|
Lambing
|
50
|
d8+4
|
d10+4
|
01 – 27
|
28 – 54
|
55 – 00
|
44
|
06:02:00 AM
|
06:19:00 PM
|
|
Blossoms
|
70
|
d10+6
|
d8+4
|
01 – 20
|
21 – 55
|
56 – 00
|
42
|
05:14:00 AM
|
06:49:00 PM
|
|
Plantings
|
72
|
d10+6
|
d10+6
|
01 – 20
|
21 – 53
|
54 – 00
|
42
|
04:35:00 AM
|
07:20:00 PM
|
|
Low Summer
|
78
|
d8+8
|
d6+6
|
01 – 20
|
21 – 60
|
61 – 00
|
36
|
04:22:00 AM
|
07:42:00 PM
|
|
Mid Summer
|
85
|
d6+8
|
d6+6
|
01 – 20
|
21 – 61
|
62 – 00
|
34
|
04:29:00 AM
|
07:40:00 PM
|
|
High Summer
|
83
|
d6+4
|
d6+6
|
01 – 22
|
23 – 62
|
63 – 00
|
33
|
04:35:00 AM
|
07:39:00 PM
|
|
Reaping
|
80
|
d4+6
|
d6+6
|
01 – 25
|
26 – 60
|
61 – 00
|
33
|
05:03:00 AM
|
07:02:00 PM
|
|
Casking
|
76
|
d8+6
|
d8+6
|
01 – 33
|
34 – 54
|
55 – 00
|
33
|
05:32:00 AM
|
06:20:00 PM
|
|
Frostflowers
|
65
|
d10+5
|
d10+5
|
01 – 35
|
36 – 60
|
61 – 00
|
36
|
06:02:00 AM
|
05:31:00 PM
|
|
Snowflowers
|
54
|
d10+6
|
d10+4
|
01 – 20
|
21 – 50
|
51 – 00
|
40
|
06:36:00 AM
|
04:55:00 PM
|
|
Darkmoon
|
40
|
d8+5
|
d20
|
01 – 25
|
26 – 50
|
51 – 00
|
43
|
07:09:00 AM
|
04:46:00 PM
|
note: sunrise and sunset times are for mid month. Terrain and weather can affect when PCs see the sun, obviously.
Third (no precipitation) – Determine Wind Speed and Direction: Wind speed is determined by a roll of d20-2 (results of less than 0 are 0). For direction (this is where the wind is coming from) use the following charts:
East of the Stone Hills (1d6)
1
West
2-3
Northwest
4
North
5
Northeast
6
East
West of the Stone Hills (1d6)
1-2
West
3-4
Northwest
5
Southwest
6
North
On both charts add +1 from Frostflowers through Brightsun.
Third (precipitation) – Determine the Type of Precipitation: Consult the following chart to determine the type of precipitation. The precipiration will begin based upon the cloud cover: clear = late afternoon/evening; partly cloudy = around Noon; cloudy = early morning.
|
Dice Roll
|
Weather
|
Min. Temp
|
Max. Temp
|
Continue?
|
Rainbow?
|
|
01 – 02
|
Blizzard, Heavy
|
|
10
|
5
|
|
|
03 – 05
|
Blizzard
|
|
20
|
10
|
|
|
06 – 10
|
Snowstorm, heavy
|
|
25
|
20
|
|
|
11 – 20
|
Snowstorm, light
|
|
35
|
25
|
1
|
|
21 – 25
|
Sleet Storm
|
|
35
|
20
|
|
|
26 – 27
|
Hailstorm
|
|
65
|
10
|
|
|
28 – 30
|
Fog, heavy
|
20
|
60
|
25
|
1
|
|
31 – 38
|
Fog, light
|
30
|
70
|
30
|
3
|
|
39 – 40
|
Mist
|
30
|
|
15
|
10
|
|
41 – 45
|
Drizzle
|
25
|
|
20
|
5
|
|
46 – 60
|
Rainstorm, light
|
25
|
|
30
|
15
|
|
61 – 70
|
Rainstorm
|
25
|
|
45
|
20
|
|
71 – 84
|
Rainstorm, heavy
|
30
|
|
15
|
20
|
|
85 – 89
|
Thunderstorm, light
|
35
|
|
15
|
20
|
|
90 – 94
|
Thunderstorm
|
40
|
|
20
|
20
|
|
95 – 97
|
Thunderstorm, heavy
|
45
|
|
10
|
15
|
|
98 – 99
|
Tropical Storm/Hurricane*
|
55
|
|
5
|
5
|
|
100
|
Special
|
|
|
|
|
- •
only East of the Stone Hills – elsewhere, treat as Gale
If the result of 'special' is rolled see the separate chart.
Then see the following chart for specifics of the precipitation:
|
Weather
|
precip (inches)
|
Duration
|
wind spd
|
move
|
vision
|
Track
|
Lost +
|
|
Blizzard, Heavy
|
2d10 + 10
|
3d8 hrs
|
6d8 + 40
|
One-eighth
|
2'
|
No
|
50
|
|
Blizzard
|
2d8 + 8
|
3d10 hrs
|
3d8 + 36
|
One-fourth
|
10'
|
-40
|
35
|
|
Snowstorm, heavy
|
2d8 + 2
|
4d6 hrs
|
3d10
|
One-half
|
one half
|
-25
|
20
|
|
Snowstorm, light
|
d8
|
2d6 hrs
|
4d6
|
Three-fourths
|
Three-fourths
|
-10
|
10
|
|
Sleet Storm
|
1d2
|
d6 hrs
|
3d10
|
Three-fourths
|
Three-fourths
|
-10
|
5
|
|
Hailstorm*
|
1d3 – 2
|
d4 hrs
|
4d10
|
Three-fourths
|
normal
|
-10
|
10
|
|
Fog, heavy
|
damp
|
d12 hrs
|
d10 - 2
|
One-fourth
|
2'
|
-60
|
50
|
|
Fog, light
|
damp
|
2d4
|
d8 - 2
|
One-half
|
One-fourth
|
-30
|
30
|
|
Mist
|
dew
|
2d6 hrs
|
d10 - 1
|
normal
|
normal
|
-5
|
|
|
Drizzle
|
dew to 1
|
d10
|
d20-2
|
normal
|
normal
|
-1/turn (cum)
|
|
|
Rainstorm, light
|
d3
|
d12 hrs
|
d20
|
normal
|
normal
|
-10/T (cum)
|
|
|
Rainstorm
|
1d6
|
d12 hrs
|
2d12
|
normal
|
normal
|
-10/T (cum)
|
5
|
|
Rainstorm, heavy
|
d4 + 3
|
d12 hrs
|
2d12 + 10
|
Three-fourths
|
Three-fourths
|
-10/T (cum)
|
10
|
|
Thunderstorm, light
|
d6+1
|
d3 hrs
|
3d10
|
Three-fourths
|
Three-fourths
|
-10/T (cum)
|
10
|
|
Thunderstorm
|
d8
|
d4 hrs
|
4d10
|
Three-fourths
|
Three-fourths
|
-10/T (cum)
|
10
|
|
Thunderstorm, heavy
|
d8+3
|
d3 hrs
|
34d10+6
|
One-half
|
One-half
|
-10/T (cum)
|
15
|
|
Hurricane
|
d10/day
|
d4 days
|
7d10+70
|
One-fourth
|
One-fourth
|
No
|
30
|
|
Gale
|
d8/day
|
d3 days
|
6d8 + 40
|
One-fourth
|
One-fourth
|
No
|
20
|
Notes:
Hailstorms have a 20% of causing 1 h.p. damage per full turn of exposure to people with less
than A.C. 5 who do not have shelter. Rings, bracers, etc. do not count, magic armor does.
During Thunderstorms there is a 1% chance per turn of a lightning bolt striking the party. +10%
if the party is under a tree, on a hill in metal armor, etc. Damage is 6d6, save for half.
For high winds see the Control Winds spell
Then modify the results with this terrain chart:
|
Terrain
|
Temp Mod
|
Wind Mod
|
|
Hills
|
none
|
plus or minus 5*
|
|
Light Forest
|
none
|
Minus 5
|
|
Heavy Forest
|
-5
|
Minus 10
|
|
Plains
|
none
|
Plus 5
|
|
Brambles or Briars
|
plus or minus 5**
|
Minus 5
|
|
Mountains
|
Minus 3 per 1,000'
|
Plus 5 per 1,000'
|
|
Sea Coast^
|
none
|
Plus 5
|
|
At Sea
|
none
|
Plus 10
|
**plus in Summer, minus in Winter
^within 20 miles of the ocean shoreline
Special Weather: If a Special event was rolled, consult this chartto determine the type of special weather event:
|
|
Hills
|
Forest
|
Plains
|
Briars
|
Mntns
|
Coast/At Sea
|
|
Special Event
|
d6
|
d4
|
d4
|
d4
|
d4
|
d4
|
|
Wind Storm
|
1
|
1
|
1
|
1
|
1
|
1
|
|
Quicksand
|
|
2
|
2
|
|
|
|
|
Dust Storm
|
2
|
|
|
|
|
|
|
Flash Flood
|
3
|
|
|
2
|
|
|
|
Rock Avalanche
|
4
|
|
|
|
2
|
|
|
Tornado
|
5
|
3
|
3
|
3
|
|
2
|
|
Snow Avalanche
|
|
|
|
|
3
|
|
|
Earthquake
|
6
|
4
|
4
|
4
|
4
|
|
|
Undersea Volcano
|
|
|
|
|
|
3
|
|
Tsunami
|
|
|
|
|
|
4
|
and then this chart to see the effects of the special weather event;
|
|
Precip
|
Wind
|
Duration
|
Move
|
Vision
|
Track -
|
lost
|
damage and effects
|
|
Special Event
|
|
|
|
|
|
|
|
|
|
Wind Storm
|
n/a
|
8d10+20
|
d10 hrs
|
One-eighth
|
One-half
|
50
|
30
|
as Control Winds spell
|
|
Quicksand
|
n/a
|
n/a
|
n/a
|
no
|
n/a
|
n/a
|
n/a
|
save vs wands or stick and begin to sink*
|
|
Dust Storm
|
n/a
|
5d10
|
d8 hrs
|
One-eighth
|
1'
|
no
|
80
|
1 dam per hour if not sheltered
|
|
Flash Flood
|
n/a**
|
Nn/a
|
3d10 rnds
|
n/a
|
n/a
|
70
|
n/a
|
if in flood 2d20 dam, save vs wand for half
|
|
Rock Avalanche
|
2d10 min
|
n/a
|
d8 min
|
n/a
|
n/a
|
60
|
n/a
|
save vs. death or crushed; 2d20 dam
|
|
Tornado
|
1/hr
|
3d100+100
|
2d10 hrs
|
One-third
|
One-half
|
no
|
40
|
if directly hit as double strength Djinn
|
|
Snow Avalanche
|
5d10 min
|
n/a
|
d10 min
|
n/a
|
n/a
|
60
|
n/a
|
d10+4 dam, save or buried
|
|
Earthquake
|
n/a
|
n/a
|
1 rnd
|
n/a
|
n/a
|
50
|
n/a
|
as Earthquake spell
|
|
Undersea Volcano
|
n/a
|
n/a
|
d10 days
|
n/a
|
n/a
|
n/a
|
n/a
|
new island at end; 20% tsunami
|
Next (precipitation) – Determine if it Continues: At the end of precipitation's duration; if the result is less than the Duration chance consult this chart;
1 Down one step on precipitation chart
2-9 roll duration again and continue
10 up one step on the precipitation chart
If precipitation continues, worsens, etc. the temperatures will change as needed to min/max levels.
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