Is there any issue in doing it this way (inspired by this post):
DayWmax(t::DayWeather) = (tmax = t.temp.max, humidity = t.humidity, windspeed = t.wind_speed) # assessor function
df = DataFrame(DayWmax.(fetch_weather(url, params).daily))
8×3 DataFrame
Row │ tmax humidity windspeed
│ Float64 Int64 Float64
─────┼──────────────────────────────
1 │ 83.97 74 7.9
2 │ 86.41 58 9.42
3 │ 86.36 64 12.71
4 │ 84.34 67 11.34
5 │ 85.37 69 9.69
6 │ 86.45 66 9.51
7 │ 87.64 59 9.42
8 │ 87.93 60 10.85