I'll chime in here having just bought a pair of riding pants.
I didn't think I'd need them. I was too cheap to buy them. Jeans seemed fine to me.
Then people I knew and liked starting falling down (wrecking) and the photos of the damage were... unpleasant. I was fortunate enough to see a full speed wipe out (35+mph) by a guy on a beemer. He slid about 25-30 yds at a minimum. After coming to a stop he got up. And walked away. He had FULL gear on. It was all textile material with appropriately placed armor. He even had a piece of separate back armor. Other than being dirty... his armor looked fine. No rips. No tears.
What's better... his skin looked fine. He'd have bruises for sure... but no loss of flesh. No road rash.
Ok. I, like you, was worried about heat in the summer (I rode two years in Texas). I wanted a pair of pants that 'did it all'. They had to fit right (snug). they had to be waterproof (haven't tested this yet, but heard its true). They had to be warm in the cool weather, and cool in the warm weather.
I found the tourmaster venture air riding pants for 140.00 with 2-day shipping. They're mesh, armored, have a waterproof liner, a thermal liner, they're silver (come in black too), they fit snug, the construction is A-rate, they're comfy, they have reflective piping, easy on/off (about 10-seconds in a hurry). Some might not like having to zip in separate liners for waterproof/thermal protection... <shrug> ... I don't mind only takes a minute to get the liners in/out. I think I might have just found the magical '4-season' riding pants.
Follow the sizing chart on the tourmaster website and you can't go wrong. I've got a 35ish inch waist and 32" inseam. The large fits perfect over a set of jeans with/without the liner.