Not sure how you retrieve you weather info but Ill show an example using a ADODB recordset. I am a C# programmer but Ill use VBS for readabiltiy. I know the actual code will look nothing like this and you probobly dont get the info from a recordset. And you are programming PHP and not ASP or VBS. But here is to demonstrate what "could" be done.
DIM SunInfo as string
DIM SatInfo as string
DIM SQLtext as string
DIM objrec as ADODB.Recordset
DIM objconn as ADODB.Connection
objconn.open "Connection info"
SunInfo = "Sun: Info not available"
SatInfo = "Sat: Info not available"
SQLtext = "SELECT Day, weatherinfo FROM weathertable WHERE" & _
" Day = 'Sunday' OR Day = 'Saturday'"
set objrec = objconn.execute(SQLtext)
do while not objrec.eof
if objrec("Day") = "Sunday" then Suninfo = "Sun: " & objrec("weatherinfo")
if objrec("Day") = "Saturday" then Suninfo = "Sun: " & objrec("weatherinfo")
response.write("Today: " & TodayInfoVariable & "<br>")
response.write(SunInfo & "<br>")
response.write(SatInfo & "<br>")
Obviosly its a lil more complex then that, but im just trying to say what I mean. I left out the table HTML for bevity.
So why not just print out the data isnt available if it isnt?