Rotom-W: Rotom-Wash has been shown to be quite the defensive pivot. With it's good base 107 defense stat and it's ability to pretty much burn every thing it wishes to burn it is a very powerful weather defensive Pokemon working both inside and outside of weather. It is often used in Sand or Rain teams to make lives miserable. Can be found in the Lost Hotel every Tuesday and can change to it's Wash form on the second floor of Professor Sycamore's Lab
Rotom-H: Rotom-H works in a very similar manner as Rotom-W however unlike it's companion it wields the Fairy resistance making it like one of the best checks to Mega Mawile(unless that monster is carrying Stone Edge) Can be found in the Lost Hotel every Tuesday and can change to it's Heat form on the second floor of Professor Sycamore's Lab
Hippowdon: Hippowdon, the classic Hippo of sand and Tyranitar's best friend. It is often overlooked and presides in the shadows of it's reptilian equal however what is often not seen is it's great base 118 Def stat and base 108 HP stat making it an excellent weather wall. Being graced to set up it's own weather of preference it works at is best in sand which it . automatically carries with it. Can be caught as a Hippopotas at route 9.
Skarmory: I am sure you might have already seen this Bird-O-Steel in action before but that base 140 Def stat is really nothing to laugh at for a smile will often turn into a frown hitting the ground whenever you realize that your physical attackers can't touch it. Best of all is that it is even easily obtainable at Victory Road or in a Friend Safari.
Chesnaught: Hey look, it's a starter. Chesnaught being the most relaible bulky starter( I am aware that Delphox can be used to surprisingly bulky prowess). It wields such a wonderful defensive movepool and stands with it's chest high with that base 122 Def stat and bountiful resistance. Funniest of all is when Talonflame comes in an expects to kill this mammal with an unboosted Brave Bird. Sometimes it is even sad... Obtained as a starter or at the Friend Safari.
You know, I don't really think you want to see a text for every single Pokemon so I think I will just continue with the plain list from here ._.
- Slowbro: Base 110 Def stat. Multi-weather defensmon. Can be caught as a Slowpoke in a horde at route 12.
- Gliscor: Base 125 Def. Sand defensmon. Can be caught in a horde as a Gligar at route 10 or in a Friend Safari with a greater chance of it having it's Hidden Ability making it a through stalling wall.
- Ferrothorn: base 131 Def. Rain and Sand defensmon. Can be caught at the Reflection Cave as a Ferroseed. Requires breeding to utilize it's common role as a Hazard Setter.
- Gyarados: Base 118 Def with Intimidate Atk drop counted in. All around Rain/Sand potential defensmon. Can be caught at route 3 and route 22 with a Super Rod
- Tyranitar: Base 110 Def stat. Sand defensmon. Can be caught at Victory Road in Pokemon Y as a Pupitar and in Pokemon X it can be caught in a Friend Safari as a Pupitar.
- Aggron: Base 180 Def.Sand defensmon and potential rain one as well. Can be caught in the Victory Road as a Lairon in X and can be caught in the Friend Safari as a Lairon.
Friend Safari exclusives
Mandibuzz: It is physically almost unbreakable. With access to Roost, Taunt, Knock Off, Foul Play and a lot more it is capable of stalling physical walls or turning their own power against them while recovering health. It usually finds itself on Sand and Rain teams but is pretty much a multi-weather wall
Bronzong: This little rust bell is often, very often looked down upon but it has magnificent potential, especially in sand. However like most of the Pokemon on this list it is a supporter and wields more of a supportive movepool. Wielding a nice base 116 Def and SDef stat it has 2 things going for it making it sponge not only physical but also special attacks.
Dusclops: Base 130 Def. Multi-weather defensmon and excellent spinblocker.
Following pages shows in which Safari they can be caught in
These are some weather Pokemon I could think off with great defensive capabilities in all/respectable weathers.