the temperature starting goes down in the end of october, if we lucky might be earlier than that.

there are no rainny season in Doha. You lucky if you get rain twice in a year. You might get rain around jan/feb time. The temperature might drop to single digit. During is OK, but u might need a light jumper during the night.

i notice u r from Singapore, if you never been to middle east before, be prepare with cultural shock. lol...