Where is the wind gauge placed and when is it read for the long jump and triple jump?

Under the World Athletics Technical Rules, the field events referee ensures the wind gauge is placed 20m from the take-off line. The measuring plane is 1.22m ± 0.05m high and not more than 2m from the runway.

Wind velocity is measured for 5 seconds from the time an athlete passes a mark placed alongside the runway: 40m from the take-off line for the long jump and 35m for the triple jump. If an athlete runs less than 40m or 35m, as appropriate, the wind is measured from the time they commence their run.

Source: https://worldathletics.org/about-iaaf/documents/book-of-rules (Technical Rules, horizontal jumps, wind measurement)