Perfectly normal in your climate, unfortunately!  If I were you I'd run
straight 40w oil during the summer, then change to straight 30w after
the 100+ degree days are over.  Two oil changes a year (or every 5000
miles), and you don't need multi grade oil in your climate.  A 40w oil
is physically thicker than a 20w-50 multi, and will give you better oil
pressure and bearing protection in your extremely hot climate.
--
Stuart MacMillan
Seattle

'84 Vanagon Westfalia w/2.1
'65 MGB (Driven since 1969)
'74 MGB GT (Restoring)

Assisting on Restoration:
'72 MGB GT (Daughter's)
'64 MGB (Son's)

Parts cars:
'68 & '73 MGB, '67 MGB GT