I try to deploy some weatherdata to the cloud but with FormFunction or FormPAge doesnt work.

CloudDeploy[
 FormPage[{"Latitude" -> "Number", "Longitude" -> "Number"}, 
  DateListPlot[{WeatherData[{#Latitude, #Longitude}, 
      "MaxWindSpeed", {{1990}, {2015}, "Month"}], 
     WeatherData[{#Latitude, #Longitude}, 
      "MaxWindSpeed", {{1990}, {2015}, "Year"}]}, Joined -> True, 
    PlotRange -> Automatic, PlotTheme -> "Web", 
    PlotLegends -> {"Monthly Maxima", "Yearly Maxima"}] &]]

The plot should be look like this:

DateListPlot[{WeatherData[{myLatitude, myLongitude}, 
   "MaxWindSpeed", {{1990}, {2015}, "Month"}], 
  WeatherData[{myLatitude, myLongitude}, 
   "MaxWindSpeed", {{1990}, {2015}, "Year"}]}, Joined -> True, 
 PlotRange -> Automatic, PlotTheme -> "Detailed", 
 PlotLegends -> {"Monthly Maxima", "Yearly Maxima"}]

I can deploy the plot properly with CloudDeploy, so as creating a CloudObject. But as soon as I try to force it to run as API through the FormFunction or FormPage the server answer is just text. Like this but with length of 2 pages:

Legended[Graphics[{{}, {{{}, {}, {Hue[0.67, 0.6, 0.6], Directive[PointSize[0.007333333333333334], RGBColor[0.790588, 0.201176, 0.], CapForm["Butt"], AbsoluteThickness[3]], Line[{{2.8401408^9, 64.82}, {2.8428192^9, 46.49}, {2.8452384^9, 42.41}, {2.8479168^9, 88.9}, {2.8505088^9, 46.49}, {2.8531872^9, 46.49}, {2.8557792^9, 37.04}, {2.8584576^9, 37.04}, {2.861136^9, 40.74}, {2.863728^9, 48.15}, {2.8664064^9, 40.74}, {2.8689984^9, 110.75}, {2.8716768^9, 74.08}, {2.8743552^9, 55.37}, {2.8767744^9, 55.37}, {2.8794528^9, 64.82}, {2.8820448^9, 55.37}, {2.8847232^9, 46.49}, {2.8873152^9, 46.49}, {2.8899936^9, 75.93}, {2.892672^9, 38.89}, {2.895264^9, 37.04}, {2.8979424^9, 40.74}, {2.9005344^9, 46.49}, {2.9032128^9, 40.74}, {2.9058912^9, 48.15}, {2.9083968^9, 64.82}, {2.9110752^9, 46.49}, {2.9136672^9, 59.08}, {2.9163456^9, 46.49}, {2.9189376^9, 46.49}, {2.921616^9, 42.41}, {2.9242944^9, 40.74}, {2.9268864^9, 37.04}, {2.9295648*^9, 46.49},

What can be the problem?

And why there is no any description about FormPage, ...I just found in a blog or discussion on the web but Wolfram documentation has no info about that. It is a really nice solution for cloud deployment since the server response is right below the form. So the user doesn't need to refresh, or go back or whatever with the page.

Thank you