Total rainfall = number of months × average per month.<br><br>
• Total for Jan&ndash;May (5 months) = 5 × 84 = 420 mm<br>
• Total for Jan&ndash;Jun (6 months) = 6 × 90 = 540 mm<br>
• June rainfall = 540 − 420 = 120 mm<br><br>
Final Answer: 120 mm