The long, cold winter had a profound impact on almost every aspect of life in the Soviet Union. It affected where and how long people live and work and what kinds of crops are grown and where they are grown (no part of the country has a year-round growing season). The length and severity of the winter, along with the sharp fluctuations in the mean summer and winter temperatures, imposed special requirements on many branches of the economy: in regions of permafrost, buildings must be constructed on pilings, and machinery must be made of specially tempered steel; transportation systems must be engineered to perform reliably in extremely low and high temperatures; the health care field and the textile industry are greatly affected by the ramifications of six to eight months of winter; and energy demands are multiplied by extended periods of darkness and cold.