These are the 2 weather observations around the time they crashed at Van Nuys Airport:
METAR KVNY 261851Z 00000KT 2 1/2SM HZ OVC014 13/09 A3018
RMK AO2 SLP218 T01280089=
METAR KVNY 261751Z 00000KT 2 1/2SM HZ OVC013 12/09 A3016
RMK AO2 SLP212 T01220089 10122 20111 51010=
2.5 miles of visibility, haze, and overcast at 1300 feet. Visual conditions are 3 miles. He requested a special VFR clearance, which allows you to fly down to 1 mile visibility, which isn't smart in mountainous terrain. If he just flew on an instrument flight plan, they would be alive.