Problems with search on chart

I saw this command and tried to imitate it sourcetype="wind" | eval intscale="SCALE"+tostring(floor(scale/10)*10) | chart count over month by intscale | sort by month

What is wrong with my command ? Anybody can guide me ? I would like to show temperature(Y-axis) on monthly (X-axis).

sourcetype="CurrentWeatherSG" | chart count over hour by mean(current_temperature)

I only tried this sourcetype="CurrentWeatherSG" | chart max(current_temperature) as Max, min(current_temperature) as Min over _time but the _time is all ... ... ... I wanted to show the numbers on X-axis.