Are you looking to network control systems or PC's?
For control systems requiring a little less bandwidth, Microwave Data Systems makes an ethernet radio that is industrially hardened, and provides 512K bandwidth over the air.
I have not seen an industrial 802.11X type router on the market.
If you need the 802.11X, you could mount the radio inside an airconditioned invironment (office), and run an external antenna to the harsher environment. Otherwise, you may need to mount an insulated NEMA-4 enclosure with a small air conditioner on the side. Look into Hoffman enclosures, they have some with aircon.