In this paper we introduce fuzzy versions some rule based lot sizing heuristics for the dynamic lot-sizing problem with warm/cold process. In our setting "the demand at each period" and "the warm system threshold" (production/order quantity required for keeping the system warm on to next period) are fuzzy numbers. Similar to the crisp counterpart setting of the problem, horizon length, production capacity at each period, inventory carrying cost and warming cost are the parameters with crisp values. The objective is to find the cost minimizing production scheme throughout the horizon. The rule based fuzzy heuristics we introduce are: "fuzzy silver meal algorithm", "fuzzy part period algorithm", and "fuzzy least unit cost algorithm". We illustrate implementation of proposed heuristics through examples. In a numerical study we present comparison results of heuristics based on various performance criteria. (C) 2016 Elsevier B.V. All rights reserved.