I've been seeing them in droves for the past couple of weeks in the N.E. Anaheim
area, all heading in a northerly direction. I have had trouble identifying them, too, if
that is any solace :) I concur that they don't look like Monarchs. Too light in color.

This is amazing.  I've lived in Orange County for over 20 years and
I've never seen THIS many butterflies.  It's eerie.  All heading North.
I'm going to start reading up on the signs of the apocalypse - cuz
damn.

I saw a whole heck of a lot of Painted Ladies from Bakersfield to Mohave
making a mess of my windshield a couple weeks ago. I don't know if they
were migrating.
http://www.edgehill.net/1/?SC=go.php&DIR=California/Desert/2005-03-19-mohave&PG=
2&PIC=6
http://www.edgehill.net/1/?SC=go.php&DIR=California/Desert/2005-03-19-mohave&PG=
2&PIC=7

Hmm:
http://www.sdnhm.org/fieldguide/inverts/paintedlady.html
"They survive through the winter in the southwestern United States, Baja
California, and Sonora. Farther north, the first frost destroys the
populations and might stimulate some to migrate south for the winter,
but this does not happen regularly.

If adequate rain occurs in the winter it can stimulate a northerly
dispersal and repopulation of the butterflies in the United States,
Canada, and Iceland. This spring dispersal can sometimes be quite
phenomenal, with millions moving through a region over a seven to eight
week period. They come to rest for a quick nectar break on a diversity
of plants before continuing their northward movement."

Lakewood checking in with swarm sightings.
Went to Trader Joe's the other day in Cerritos
and on the way back, we drove through a large
swarm of small butterflies going North. I mean
the butterflies were going North, I was going west.
There were hundreds of them. I'm seeing about 2 or 3
per minute going over my house for the last couple days.
They are just what you described. See image here:
http://www.photosig.com/go/photos/view?id=1471006&forward=main
Cheers and Happy Easter.

My brother, sister in law, and mother in law drove over to San Diego from
the Phoenix, AZ area for Easter weekend - their car was covered with the
little butterflies described in the various postings.  They returned to AZ
on Monday - and again - their car was plastered with them.  They inquired
at a service station about this odd phenomenon and it was suggested that
the heavy rains this winter are responsible for the enormous population of
butterflies!  We wanted to know the name of this butterfly?  Other postings
have mentioned Painted Lady.  Much, much too small for a Monarch or Viceroy
- although the coloration is quite similar.