Clause 6.2 provides the basic wind speed (Vb) for India through the wind speed map (Fig. 1). The map divides India into 6 wind zones with basic wind speeds of 33, 39, 44, 47, 50 and 55 m/s. Vb is the peak gust speed averaged over a short time duration of about 3 seconds at 10 m height above mean ground level in open terrain (Category 2). It is based on a 50-year return period. For important structures or different design lives, Vb is modified by the risk coefficient k1.
Key Requirements
•Basic wind speed shall be obtained from the wind speed map (Fig. 1) or from Appendix A for specific cities
•Vb corresponds to peak gust speed at 10 m height in terrain Category 2 with 50-year return period
•For coastal areas within 10 km of the sea, the wind speed shall not be taken less than 39 m/s
•Where local records from nearby anemograph stations are available, they may be used with adjustments for terrain, height, and averaging time
•For cyclonic regions (as defined in IS 875 Part 3), higher basic wind speeds apply per Appendix B
Reference Tables
Basic Wind Speed Zones of India (Fig. 1, Clause 6.2)
Coastal Odisha, coastal Andhra, coastal Tamil Nadu
VI
55
198
Coastal Gujarat (Dwarka–Porbandar), parts of Andaman & Nicobar
Speeds are 3-second gust speeds at 10 m height in open terrain (Category 2). For exact values at any location, refer to IS 875 Part 3 Fig. 1 or Appendix A.
Practical Notes
✓Most of inland India (Delhi, Bangalore, Hyderabad, Jaipur) falls in Zones I–II (33–39 m/s). Coastal cities are typically Zone IV–V (47–50 m/s).
✓The 2015 revision updated wind speeds for several cities — always use the 2015 map, not the old IS 875:1987 values.
✓For buildings on hilltops or ridges near the coast, the combination of high Vb and k3 > 1.0 can produce very high design wind speeds.
✓Wind speed contours change steeply near the coast — a site just 5 km inland can have a significantly lower Vb than one right on the shore.
Common Mistakes
⚠Using old IS 875:1987 wind speed values instead of the 2015 revision — several cities have updated speeds.
⚠Taking Vb less than 39 m/s for coastal sites within 10 km of the sea, which violates the code minimum.
⚠Confusing 3-second gust speed (IS 875) with hourly mean speed (some international codes) — Vb in IS 875 is a gust speed.
⚠Not checking Appendix A for the specific city and instead interpolating loosely from the map.