During rain season (september-december) the rain can be very furious and intense, that is the reason because streets become into deep rivers and turn your car into a light boat. so be careful where not to drive if it is raining, ask some local for help, and belive me, you gonna give thanks for the advise!.
Well i think as a big city, it exists the general problems as in any big city, about food, well you might be careful with vegetables and water.
Oh! it´s too hot in there on Summer and almost in anytime of the year and too cold on winter. If you thought it was hot on Mexico beaches, you havent feel anything! Monterrey is like SO HOT!!!
All the year weather is so hot, about over 100 F in summer, winter is short and killer. Get plenty of water, t shirts, etc. You don´t like to turn into this: