Some of the free pdf-adventures from Wizards have various side-bars about conditions and such. This one, by Monte Cook, has some info on freezing water:
A Frigid Demise
Another one,
Into The Frozen Waste by Eric Cagle, has this to say about winter conditions:
Weather and Terrain
Into the Frozen Waste takes place in subarctic conditions,
where the temperature is often below freezing. In addition to
monsters, the characters must contend with bitter cold, difficult
terrain, and icy conditions. The DM should be familiar with the
rules for cold, wind, precipitation, and other environmental factors,
as described in Chapter 3: Running the Game in the DUNGEON
MASTER’s Guide. Below are some of these rules that may
come into play.
Cold Dangers: Cold and exposure deal subdual damage. Hit
points lost in this way cannot be recovered until the afflicted
character gets out of the cold and warms up again.
Once a character has been rendered unconscious from cold
damage, the cold and exposure deal normal damage at the
same rate. An unprotected character in cold weather conditions
must make a Fortitude saving throw each hour (DC 15, +1 per
previous save) or take 1d6 points of subdual damage.
A character who is submerged in freezing water must immediately
make a Fortitude save (DC 20) or take 1d6 points of subdual
damage per round that he or she remains in the water. A
character with the Wilderness Lore skill may receive a bonus on
this saving throw, and this bonus may apply to other characters
as well.
A character who takes any subdual damage from cold suffers
from frostbite or hypothermia (treat as the fatigued condition;
see page 84 of the DUNGEON MASTER’s Guide). Characters
should purchase winter clothing or get magic items that prevent
cold damage.
Snow: While falling, snow reduces visibility as though it were
rain (–4 penalty on Spot checks, Search checks, and attack rolls
with ranged weapons). The snowy and icy terrain of an ice floe
reduces movement by half.
Ice: Any character walking on slippery ice must make a successful
Balance check (DC 15) to avoid slipping and falling.
Over long distances, such a character must make a check each
minute.
Snowshoes and Ice Crampons: A character wearing snowshoes
(10 gp) can move at three-quarters of normal speed on
snowy terrain. Ice crampons (10 gp) reduce the DC for the Balance
check to walk on ice by 5. Each of these items also
imposes an armor check penalty on the wearer (–2 for snowshoes
or –1 for ice crampons), which stacks with any other
applicable armor check penalties. A character cannot wear
snowshoes and ice crampons at the same time. It takes a fullround
action to don or remove either ice crampons or
snowshoes.
Weather: The weather can be just as much of an enemy to the
characters as monsters are. The DM should make judicious use
of Table 3-19: Random Weather on page 89 in the DUNGEON
MASTER’s Guide, using the “cold climate” heading.
