The central region of the European part of the Soviet Union is one of the most highly developed and densely populated areas of the country. Agriculture includes a wide range of major crops, highly productive livestock farming, and numerous industrial enterprises, primarily processing industries. Resolutions adopted by the Party and the Government provided for a series of major measures aimed at increasing crop yields, expanding cultivated areas, increasing livestock numbers, and improving productivity. In order to increase the output of grain crops, industrial crops, and oilseed crops in the central region of the European part of the Soviet Union (as well as in other regions), plans were made to extend the cultivation of certain crops northward and to expand the acreage devoted to winter and spring wheat, buckwheat, millet, legumes, feed grains (maize, barley, and oats), sugar beet, flax, hemp, and sunflower. To ensure the successful development of animal husbandry and the establishment of a stable fodder base, cultivated areas were also expanded, and measures were introduced to increase the yields of perennial and annual forage grasses, silage maize and sunflower, potatoes, fodder root crops, and fodder melons. New orchards and berry plantations were being established throughout the region, with the planting of cold-resistant Michurin varieties of apples, pears, plums, cherries, and berry crops. In the suburban zones of major industrial centers, the production of potatoes and vegetables increased sharply, while dairy farming, pig breeding, poultry farming, and fruit growing also expanded. The Party's and Government's measures for the socialist transformation of agriculture were based on the northward extension of certain crops, the application of advanced agricultural technology, and the utilization of previously undeveloped lands, including floodplains, lowlands, and drained peatlands. In the course of agricultural transformation, in addition to a series of organizational measures, it is essential to take accurate and detailed account of the natural geographical characteristics of farm locations, particularly their soil and climatic conditions, and in many cases the microclimate of individual fields as well. At present, no comprehensive climatic description exists for the entire central region. Only the monograph by E. E. Fedorov and A. I. Baranov (1949) provides a general overview of the region’s climate in terms of weather conditions, but it does not adequately reflect the influence of climatic characteristics on agricultural production. Other climatic surveys cover only individual areas and, in most cases, fail to address the fundamental questions of modern agriculture. This work was prepared jointly by numerous staff members of the Department of Climatology of the Central Geophysical Observatory named after A. I. Voeykov and the Department of Agricultural Meteorology of the All-Union Research Institute of Crop Production. It brings together and systematizes the climatic and phenological research accumulated by the two institutions in recent years, incorporates a series of special data-processing studies, and draws upon the experience of previously published works concerning the central region. Most of the cartographic materials were newly compiled using long-term observational records from meteorological stations up to 1950, particularly data on precipitation, snow cover, and soil temperature. The climatic section of this work is based primarily on climatological reference manuals for the individual oblasts. For agricultural planning and calculation purposes, monthly averages of climatic elements alone are insufficient. It is therefore necessary to develop a wide range of indicators reflecting temporal variations in climatic characteristics. To this end, this work makes extensive use of probability estimates, expressed in two forms: probabilities of occurrence by year (used for precipitation, snow cover, and similar phenomena) and probabilities that specific periods begin before a certain date or exceed a certain duration. The latter are primarily used to characterize the onset, termination, and duration of climatic periods. The probability of occurrence is defined as the statistical recurrence frequency of an event within a long series of years, expressed as a percentage. Probability tables for most meteorological elements were compiled from long-term observational records. They indicate the frequency with which values of different classes occur under a given long-term average. For example, when the average precipitation in June is 60 mm (Table 69, Region I), there may be eight years out of one hundred with less than 20 mm of precipitation during dry years (8% probability), and twenty-four years with 20-40 mm. When the average is 70 mm, monthly precipitation of 40-60 mm occurs most frequently (23% probability), while in wet years monthly totals may exceed 120 mm (12% probability). In July, for the same region and the same average precipitation of 60 mm, the probability of receiving less than 20 mm increases to 10%. The most likely precipitation range is 20-80 mm per month, with each of the three classes accounting for approximately 22%. In the wettest years, July precipitation may also exceed 120 mm. Similar probability distributions are presented for precipitation, the depth of penetration of temperatures above 0°C, and related indicators. For periods defined by particular temperatures and frost-free conditions, probabilities are given for their beginning and ending before specified dates. For example, if the average date when the mean daily temperature rises above 0°C is April 1 (Table 4), then positive temperatures can never occur before March 6 in any year (0% probability). In two years out of one hundred, such temperatures may occur before March 11 (2% probability), while by April 26 the mean daily temperature exceeds 0°C in all years (100% probability). Probabilities for periods of different durations are presented in a similar manner. Probability tables can be used to evaluate experimental results associated with the weather conditions of particular years. For example, when assessing the possibility of extending a new crop northward, if favorable or unfavorable results are obtained during one or two years, it is necessary to determine the extent to which the year’s principal indicators (heat and moisture) deviated from long-term averages, using such measures as frost-free period length, accumulated temperatures, mean summer temperature, winter minimum temperature, and precipitation. By consulting the probability tables for these phenomena, one can determine how likely similar, better, or worse maturation conditions may be. A good harvest of a heat-loving crop during exceptionally warm years, whose recurrence probability does not exceed 10-20%, is not sufficient evidence that the crop can be successfully cultivated in a new region. Conversely, if the same result is obtained in a relatively cool year, and similar or better conditions occur with a probability of 60-70%, then there are reasonable grounds to expect successful introduction of the crop into the region under study. The probabilities associated with the occurrence of specific mean daily temperature dates may be used to determine the most appropriate starting and ending dates for field operations, as well as the most probable beginning of the growing season and other agricultural activities. To provide a more detailed characterization of thermal conditions, ten-day mean temperatures and recurrence frequencies of mean daily temperatures derived from monthly averages are presented (Appendices 3 and 5). An attempt is also made to relate mean diurnal temperature to monthly average temperature, average maximum temperature, and average minimum temperature. Particular attention is paid in this work to the positive influence of human activity on climate and to the effects of shelterbelts, irrigation, drainage, and large reservoirs on the microclimate of agricultural lands.