Would you allow it?
+30° Celsius for a Blacksmith like character for example?
Below 10° Celsius for a Character that has Butcher or something like that for a Dayjob or otherwise much time consuming activity?

Quite frankly, no, not as an allergy. A vulnerability to heat or cold, as with the critter weakness, could pass, though.

Since neither Blacksmith nor Butcher are professions PC are going to pursue regularily, though, this wouldn't really gain you many points. Depending on the character, it might even be on even level wil "severe allergy (plutonium)" or "phobia (dark side of the moon)".

I think I'd give points for a Pink Floyd phobia....

Think in astronomical terms.

I would. But only the mild and moderate strength. Fow example: I have a very high sensibility for cold, mostly due to problems with my circulatory system in my hands... and i know that i (when doing a paper route in the middle of winter) was pretty much crying and couldn't use my hands after a few minutes. But i didn't get "damaged" by it.

Also i wouldn't have fixed temperatures but would gradually assign mods depending on time, temparature and equipment... Overall: make new qualities, but use allergy as a template.

yeah, i was thinking light or moderate, so as soon as the temperature is reached, the character gets a +1 to all his target numbers.
Also, heat and/or cold based weapons would deal more damage too.

People actually can develop nettle rash in response to environmental factors like heat or cold, which is called "cold allergy" although it's not a real immune problem. And AFAIK it also is limited to such skin reactions, no anaphylactic shock etc.

Same. Seems quite reasonable.

Yes, I'd allow it.

But I encourage original thinking and interesting take on established rules. As long as all the pieces fit and the whole is reasonable, I'm all for it. This would be a prime example of exactly that type of thinking.

It's quite elegant, actually. Unusual cold and heat are circumstances that can certainly pop up in shadowruns; in laboratories, industrial facilities, burning buildings and so forth. The allergy rules cover possible effects pretty well, too.

Which means it's an allergy that will actually show up to discomfort the PC.

In terms of Allergy/Addiction/Prejudice/whatever, I think that anything that fits the Common-Rare scale and the Mild-Severe scale is fine. Anything.

I think it's a good idea as well. I know I play both Airsoft and Paintball and I have a very low heat tolerance so when I play in the Summer I don't move as fast or shoot as well. The heat also causes me to seek immediate shelter when possible, and buy cars and live in homes that are designed to stay cool (my current domicile is built with concrete walls and I drive a car that blows air conditioning through the seats).

I agree that it probably can't be purchased as severe, but I would say in real life I have a mild allergy to the heat so I'd allow it.

Well, maybe Allergy is the wrong word for it, but i was thinking about using the Allergy Rules with Heat/Cold as the Problem instead of something else.
I like to hear other peoples thoughts on such ideas. Basically, i had this idea because i have similar Problems with heat. 20°c is uncomfortable, with 25°c i get problems and on 30°c and over my body is usually close to collaps allready . . been that way all my life . . I would have to read up on the Weakness stuff, but it's something for critters or so, so i thought iw ould stay as close to the original stuff as possible with using the Allergy rules . .

With me it is many factors. The whole thing is more complex than: 0 °C and i get -2 on all actions.

For example: if i am inactive in a moderately cold room.. say 16 degrees and lower (thats CELSIUS, you barbarians *g* ). Working with the mouse and keyboard for example - i get a bit slower with my hands, but nothing serious. But in winter cold; under 0 °C i just can't keep up with supplying blood too my hands and they end up incapable of fine manipulation as well as significant speed loss and a nice bit of PAIN (a clear -4 for me). It is pretty much instant if i touch some metallic stuff at -10°C - drains my sweet body heat right out.

Now, gloves extend my time a bit... but in the end never help me that much.

So it is gradually worse, much more than a real allergy (or the ones that matter). Let just choose the player heat or cold and give gradually modifiers spanning over mild to moderate, depending on length of exposure, equipment and temperature.

Me? I LOVE the Cold.
I get much livelier, the colder it gets.
I had SO much fun this last Winter.
FINALLY! SNOW! -10° Celsius for some days!
I was in heaven! ^^
But yeah, most people seem to have more Problems with Cold than with heat.
Also, i seem to suffer from a mild case of natural suprathoid gland.
My body Temperature is usually around 38° Celisus, which is a bit above the norm i guess.
Thus i deal better with cold, but i have hellish problems with heat <.<
Also, very sensitive eyes. And a light Sunlight Allergy. Even if i am completely white from sunblock, i hold my arm into the sun for about thirty to 60 minutes, and i can watch the skin getting red.
One or two hours later, i can peel of the burned skin and underneath i get a pasty white and a bit raw new skin . . i don't tan. I go from white to red to white again in a matter of hours <.< . .
Itches and hurts like hell too . . so i usually move from shadow to shadow too in the summer . .

So I guess the trick is to decide what temp and what penalty Joe average suffers and what levels the PC that gets BPs suffers at.

Had a guy try and take phobia (vampiric buffalo).

The idea might sound strange, but you should really put on more clothes. Sweat's the best coolant. I've been shivering in this suff while we had more than 30°C in the shade and we fought some 'battles' at noon. You only get into trouble if you don't drink enough. Otherwise you're fine.

I've tried variations with gear and clothes - even the high tech wicking fabrics. For me nothing cools better than one layer of thin cotton - a black Hanes undershirt and some light rip-stop BDU pants is all I wear out there. Sure there's no protection from the pain, but getting shot doesn't hurt that bad or that long.

When players do that, I let them. Then bring in a vampiric buffalo (or even just buffalos of unknown vampiric status) every once in a while.

Even toss in a meet at Ted's Montana Grill. See if they role-play that well.

I do . . Troll, moderate allergy against common (dogs hair) and phobia light against common(dogs) . . i almost shredded a poodle with an ares viper slivergun, because it was sniffing the bushes i was hiding behind . .

A way to make it the allergy more 'severe' is to have it where its not the temperature itself that causes the modifiers, but the change. When going from the average temperature hallway into the cold morgue, there allergies get set off, and then again when they leave. So the allergy would effect them for a limited time, but whenever there is a noticeable temperature change.

I know from personal experience, this can be a hassle. I get similar symptoms to my allergies when there is a strong temperature and humidity change, to the point that my friends jokingly use me to tell when seasons are changing.

Hmm, how would this work for a character with 30° celsius and above as an allergy?
Going from hot into cold should not bother him at all. it certainly doesn't bother me.
Going from cold into hot should definitely bother him, simply because of the heat O.o
Or did you mean the character would suffer when going from cold into warmer space?
So for example, he comes out of the 5° celsius morgue into te open of 20° Celsius and suffers?

Head and cold can aggravate allergies or conditions. Skin, breathing, migraines, etc. So if my player wanted to elaborate I'd allow it. And not just because I get physically miserable in even most mild of heat. I'm a hot blooded person and prefer the cold.

Edit: From the sounds of it I should vacation with Stahlseele.