The city has no officially defined geographical limits. Since 1980s the city has expanded with fast urbanization. Mymensingh city is clearly marked by the old Brahmaputra river flowing along its north. Shambhuganj is situated on the other side of the Brahmaputra, connected by the Shambhuganj Bridge. Other ends of the city are marked respectively by the beginning of the Agricultural University campus, the Medical College, Army cantonment and, finally, Sultanabad, a township built for the followers of Aga Khan. A railway line connecting Dhaka with northern districts, built between 1885 and 1899, passes through the city and divides it into two sides.
The climate of Mymensingh is moderate, much cooler than Dhaka, as it is closer to the Himalayas. The monsoon starts in May or June and continues till August. It rains heavily and sometimes for days and weeks. During the monsoon, the temperature varies between 15 and 20 degrees. The temperature falls below 15 °C (59 °F) in winter which is spread over December and January and may well include November and February. The highest temperature is felt during April–May period, when the temperature may be as high as 40 °C (104 °F). High humidity causes heavy sweating during this period. For western travelers, the best time to visit is between November and February.