I am afraid there is no IPUMS-USA variable that directly measures temporary worker status. In IPUMS-CPS, variables such as WHYPTLWK (why part-time last week) and WHYPTLY (why part-time last year) include the categories like “seasonal work” and “slack work”, and the IPUMS-CPS variable WHYUNEMP (why unemployed) includes the category “Temporary job ended”. However, these variables do not have equivalents in IPUMS-USA. There may be a way to leverage the information available in IPUMS-USA (such as weeks and hours worked) into an approximation of temporary work status, but I am not aware of any agreed upon method. You could try looking at research that utilizes the ACS or Census (which IPUMS-USA is based on) and see if other researchers have attempted such an approximation.
I hope this helps.