Being a tidally locked planet, the weather isn’t affected by the coriolis effect. This makes it easier to predict, and brings a certain stability to the weather patterns of the planet. However, it also means that once a storm does build up, very little stands in its way.
Zones
The weather on the planet varies a lot based on how close to the sun a location is. For generalization, these cycles can be divided into four separate zones.
The Sunspot
The section closest to the sun is scorched with unending daylight. It is a barren wasteland without any vegetation. Over time, dust and particles build up here and create colossal storms that eventually break free and rampage across the wastes and towards more fertile land. Any moisture in this area is instantly evaporated and rises back out into the ice belt of the planet.
Moving outside in this heat will lead to death within minutes unless wearing heavy protection gear. Outside of rare cold storms from the other side of the planet, the temperature in this zone never falls below 50 celsius and can reach almost as high as 110.
Inhospitable Heat
While hotter than most anyone would enjoy living in, this zone won’t kill you immediately. With some preparation, it is possible to survive for most of a day before succumbing to the heat. With protection gear it would be possible to live a whole life here, though it is undesireable. The region is frequently ravaged by storms from warmer areas, making it an inhoispitable environment.
Any water is also too far down in the earth for most plants, meaning heavy use of the underground caves will be necessary for anyone trying to survive out here. The temperature vaaries some with the winds, but rarely drop below 35 celsius, normally staying around 45.
Habitable Zone
Ranging from warm to chilly, this area covers a stripe around the planet where people are able to survive without any special precautions. The still sun causes temperatures to be very constant through the region, though winds and storms from the colder and warmer areas can cause them to fluctuate some.
The zone extends further into the cold zone than the warm, as it takes a while for the chill temperatures to become so low that it prevents normal life. On the warmer side, temperatures top out around 30 celsius, but outside of the sunlight they can get as low as -20.
The Frostlands
As one gets further out from the habitable zone, the chill sets in deep, requiring warm clothing to survive even hours without an external heat source. The temperatures in this area are rarely above -25 celsius and can go as far down as -95.
Water Cycle
Because evaporating water easily escapes into space, there is little surface water on the planet. However, large oceans can be found below the ground at the surface. The planet’s gravity isn’t strong enough to pull water back down as rain, but collisions up in the discs breaks off parts of ice that sporadically makes its way down as sleet or hail.
Eventually, this water filters down through the rocky ground and ends up in the underground oceans where most of the liquid is trapped. At least until a settlement or travelling group brings it back up to the surface. Alternatively, the water hails down on the cold pole and remains there frozen in ice until a storm tears it up and brings it to a place it can melt or evaporate.
Wind
With the planet lacking rotational forces, the heat difference between the poles are the main factor creating winds. As air pressures build up on the warm side, strong winds consistently blow towards the cooler areas. This air is then again forced back towards the warmth and over time the cycle has stabilized into constant channels of wind. While the relative strengths can vary some, there is rarely any deviation in the wind direction any single area faces.
Storms are the exception to this rule. Over time, the poles develop a pressure difference which eventually erupts in a violent storm travelling from one side to the other and restoring equilibrium. Such storms can be noticed well in advance by reading the wind speeds, but it is rarely necessary as they tend to mostly calm down before reaching the habitable zone.
Hot and Cold
Depending on where the pressure builds up, the storms behave differently. The most frequent storms come from the warm side of the planet and rarely bring enough force to damage anything near the equator.
However, roughly every fifteen years, a storm from the cold pole will build up. These storms entirely upset the wind channels as they uniformly push onwards to fill in the low pressures on the warm pole. They also bring enough energy with them to do real damage to structures in the habitable zone, bringing destruction to all of civilization in one chaotic burst.