I created a new table in my database called RealtimeExtras and use the 'Custom upload - minutes interval' to insert the data from here you can extract the highs lows & averages and also graph it like here
http://www.cliftonweather.co.uk/mx/graphGrassTemp.php
All my extra sensor's go in here including my Ecowitt ones, this is the SQL I use:-
INSERT IGNORE INTO RealtimeExtras (LogDateTime,GrassTemp,LeafTemp,SoilTemp,SoilMoisture,LeafWetness,Wetbulb,Temp,Dewpoint,AvgTemp,Reception,LightningDistance,LightningTime,LightningStrikes,GreenhouseTemp,GreenhouseHum,GreenhouseDew,Temp2,Hum2,Dew2) Values('<#time format="yy-MM-dd HH:mm:ss">',<#SoilTemp1>,<#SoilTemp2>,<#SoilTemp3>,<#SoilMoisture3>,<#LeafWetness2>,<#wetbulb>,<#temp>,<#dew>,<#avgtemp>,round(<#DavisTotalPacketsReceived>/(<#DavisTotalPacketsReceived>+<#DavisTotalPacketsMissed>)*100,1),'<#LightningDistance>','<#LightningTime format="dd/MM/yy HH:mm:ss">',<#LightningStrikesToday>,<#ExtraTemp2>,<#ExtraHum2>,<#ExtraDP2>,<#ExtraTemp3>,<#ExtraHum3>,<#ExtraDP3>); CALL mainCall();