A record $23.8 billion in sales is expected to be spent by consumers for Amazon Prime Days, Adobe said in a forecast released on July 7. That's a 28.4% increase year over year and $9.6 billion more than the comparable period last year. Last year, shoppers spent $14.2 billion during the two-day Amazon Prime event, according to Adobe.

Electronics and back-to-school supplies are expected to top many shoppers' lists.