\documentclass{standalone}

\usepackage{graphicx}
\usepackage{libertine}

\usepackage[none]{hyphenat}

\usepackage{tikz}
\usepackage{ifthen}
\usetikzlibrary{arrows,arrows.meta,automata,calc,fit,matrix,positioning,fadings,shapes.geometric,intersections,shapes.arrows,shadows,decorations.markings,decorations.pathreplacing,backgrounds,circuits.logic.US,patterns}
\usepackage{tikzsymbols}

\begin{document}

\begin{tikzpicture}[every node/.style={minimum size=1cm},
  on grid, x=0.6cm, y=0.6cm]

  \def\xsize{10}
  \def\ysize{10}

  \draw[-stealth] (0, 0) -> (\xsize, 0) node[below] {Temp};
  \draw[-stealth] (0, 0) -> (0, \ysize) node[above,rotate=90] {Fan speed};

  \draw (1, 2) -- (5, 4) -- (8, 8);
  \draw[dotted] (1, 2) -- (1, 0) node[below] {T\_0};
  \draw[dotted] (5, 4) -- (5, 0) node[below] {T\_1};
  \draw[dotted] (8, 8) -- (8, 0) node[below] {T\_2};
  \draw[dashed] (1, 2) -- (0, 2) node[left] {RPM\_0};
  \draw[dotted] (5, 4) -- (0, 4) node[left] {RPM\_1};
  \draw[dotted] (8, 8) -- (0, 8) node[left] {RPM\_2};
  \draw[dashed] (8, 8) -- (9.5, 8);
  \fill[pattern=north west lines, pattern color=gray] (0, 0) rectangle (1, 2);
  \fill[pattern=north west lines, pattern color=gray] (8, 0) rectangle (9.5, 8);

\end{tikzpicture}

\end{document}
