Spring is a term of art in Minnesota. There is almost always still snow on the ground when the Twins start their season. That is a primary reason why they played in the multipurpose Metrodome with the inflatable roof to prevent snow from caving in the place. When the team, architects, and planners designed Target Field, they made a bold choice to go without a roof. The plot of land they chose had too small of a footprint to include a retractable cover like the one at Safeco Field, and the cost to build a more dome-like retractable roof like the one at Miller Park in Milwaukee was apparently just too cost-prohibitive.