Widnau is a municipality in the Wahlkreis (constituency) of Rheintal in the canton of St. Gallen in Switzerland.

Of the rest of the land, 59.4% is settled (buildings or roads) and the remainder (4%) is non-productive (rivers or lakes).

The blazon of the municipal coat of arms is Or a bar wavy Azure base seme of Tufts Vert and overall a Willow pollarded of the last eradicated and trunked Gules.

Of the foreign population, (as of 2000[update]), 153 are from Germany, 205 are from Italy, 685 are from ex-Yugoslavia, 246 are from Austria, 165 are from Turkey, and 322 are from another country.

[11] From the 2000 census[update], 4,773 or 63.9% were Roman Catholic, while 1,181 or 15.8% belonged to the Swiss Reformed Church.

The wettest month is July during which time Widnau receives an average of 159 mm (6.3 in) of rain or snow.

The month with the most days of precipitation is June, with an average of 14.2, but with only 149 mm (5.9 in) of rain or snow.

The driest month of the year is March with an average of 62 mm (2.4 in) of precipitation over 13.3 days.