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Urban green infrastructures have been extensively studied for their ability to mitigate the urban heat island (UHI) effect. However, allotment gardens (AGs)—a prominent type of urban green infrastructure within many European cities—have not yet been comprehensively investigated concerning their microclimates. In this study, nocturnal air temperatures (<inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi>N</mi> </msub> </mrow> </semantics> </math> </inline-formula>) in 13 AG complexes (AGCs) were measured during the summer of 2018 in Berlin, Germany. These were compared to measurements in densely built-up urban areas (URB), two large inner-city parks and rural areas (RUR). On average, the assessed AGCs were 2.7 K cooler at night than URB. Most of the investigated AGCs (11/13) displayed a larger mean <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi>N</mi> </msub> </mrow> </semantics> </math> </inline-formula> difference to URB (<inline-formula> <math display="inline"> <semantics> <mrow> <mover accent="true"> <mrow> <mi>Δ</mi> <msub> <mi>T</mi> <mrow> <mi>N</mi> <mo> </mo> <mi>A</mi> <mi>G</mi> <mi>C</mi> </mrow> </msub> <mo> </mo> </mrow> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics> </math> </inline-formula>) than the examined urban parks. RUR showed the largest differences to URB (<inline-formula> <math display="inline"> <semantics> <mrow> <mover accent="true"> <mrow> <mi>Δ</mi> <msub> <mi>T</mi> <mrow> <mi>N</mi> <mo> </mo> <mi>R</mi> <mi>U</mi> <mi>R</mi> </mrow> </msub> </mrow> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics> </math> </inline-formula>), indicating a UHI effect. Furthermore, the influence of land surface characteristics of the AGCs on <inline-formula> <math display="inline"> <semantics> <mrow> <mover accent="true"> <mrow> <mi>Δ</mi> <msub> <mi>T</mi> <mrow> <mi>N</mi> <mo> </mo> <mi>A</mi> <mi>G</mi> <mi>C</mi> </mrow> </msub> </mrow> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics> </math> </inline-formula> was analyzed. <inline-formula> <math display="inline"> <semantics> <mrow> <mover accent="true"> <mrow> <mi>Δ</mi> <msub> <mi>T</mi> <mrow> <mi>N</mi> <mo> </mo> <mi>A</mi> <mi>G</mi> <mi>C</mi> </mrow> </msub> </mrow> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics> </math> </inline-formula> decreased significantly as the floor space index around AGCs increased. The analysis of the shape complexity also produced a significant positive correlation with <inline-formula> <math display="inline"> <semantics> <mrow> <mover accent="true"> <mrow> <mi>Δ</mi> <msub> <mi>T</mi> <mrow> <mi>N</mi> <mo> </mo> <mi>A</mi> <mi>G</mi> <mi>C</mi> </mrow> </msub> </mrow> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics> </math> </inline-formula>. In contrast, size and distance to the city center of an AGC decreased significantly with increasing <inline-formula> <math display="inline"> <semantics> <mrow> <mover accent="true"> <mrow> <mi>Δ</mi> <msub> <mi>T</mi> <mrow> <mi>N</mi> <mo> </mo> <mi>A</mi> <mi>G</mi> <mi>C</mi> </mrow> </msub> </mrow> <mo stretchy="true">¯</mo> </mover> </mrow> </semantics> </math> </inline-formula>. This study provides first insights into the microclimate of AGs and influencing variables concerning <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mi>T</mi> <mi>N</mi> </msub> </mrow> </semantics> </math> </inline-formula>.