I would keep hops and yeast in as controlled of cold/cool temperatures as possible. I wouldn't worry about temperature with grain as long as you can keep out humidity. Keep in mind that grain grows in the summer in full sun and then sits in massive grain silos on farms, maltsters and breweries in the weather on a regular basis. Keeping grain at room temperature is not a big deal. However, you should keep grain in an animal defensive vessel so you don't have mice eating and defecating into your grain.
Your equipment will be fine at most temperatures. I wouldn't be so worried about heat unless you live in the desert but I would be worried about having your plastic or rubber get below freezing because those cold temperatures can over time cause small cracks and brittleness that will cause them to split or break. I'm sure plenty of people will point out that they keep equipment in garages that get well below freezing but it would not be my preference.