 In the West Midlands , the warmest time of the year is July and August , when maximum temperatures average around 21 ° C ( 70 ° F ) ; the coolest months are January and February , when minimum temperatures average around 1 ° C ( 39 ° F ) . The area 's average maximum and minimum temperatures are almost exactly in line with the national average . The average annual rainfall is about 676 millimetres ( 27 in ) , the wettest months being September to January . This is lower than the national average annual rainfall of 838 mm ( 33 inches ) . 
