Hi gri0,
We receive data from OpenWeatherMap API, convert measurement units and display data as it is.
You can check following request:
http://api.openweathermap.org/data/2.5/forecast/daily?mode=json&lat=10.933333&lon=108.1000000000000&lang=ru&cnt=5
And response:
{"city":{"id":1571058,"name":"Phan Thiet","coord":{"lon":108.099998,"lat":10.93333},"country":"VN","population":0},"cod":"200","message":0.0157,"cnt":5,"list":[{"dt":1437364800,"temp":{"day":301.3,"min":299.4,"max":301.3,"night":299.4,"eve":299.97,"morn":301.3},"pressure":1017.05,"humidity":82,"weather":[{"id":500,"main":"Rain","description":"легкий дождь","icon":"10d"}],"speed":2.37,"deg":215,"clouds":88,"rain":1.14},{"dt":1437451200,"temp":{"day":301.95,"min":299.1,"max":302.96,"night":299.21,"eve":302.96,"morn":299.1},"pressure":1019.79,"humidity":88,"weather":[{"id":803,"main":"Clouds","description":"пасмурно","icon":"04d"}],"speed":1.71,"deg":209,"clouds":68},{"dt":1437537600,"temp":{"day":302.7,"min":298.88,"max":305.08,"night":300.66,"eve":305.08,"morn":298.88},"pressure":1019.39,"humidity":81,"weather":[{"id":800,"main":"Clear","description":"ясно","icon":"01d"}],"speed":3.4,"deg":282,"clouds":0},{"dt":1437624000,"temp":{"day":302.09,"min":297.54,"max":302.09,"night":297.54,"eve":299.79,"morn":298.61},"pressure":998.31,"humidity":0,"weather":[{"id":500,"main":"Rain","description":"легкий дождь","icon":"10d"}],"speed":3.13,"deg":256,"clouds":70,"rain":2.22},{"dt":1437710400,"temp":{"day":303.77,"min":298.78,"max":303.77,"night":298.78,"eve":300.83,"morn":299.11},"pressure":996.16,"humidity":0,"weather":[{"id":500,"main":"Rain","description":"легкий дождь","icon":"10d"}],"speed":4.01,"deg":257,"clouds":18,"rain":2.24}]}
Two last days have humidity with zero value.
So it is not a plugin bug.