Period of the year, also called frost-free season, during which growing conditions for native vegetation and cultivated crops are the most favourable. It usually becomes shorter as distance from the equator increases. In equatorial and tropical regions the growing season ordinarily lasts all year; at higher latitudes (e.g., the tundra), it may last as little as two months or less. It also varies according to elevation above sea level: higher elevations tend to have shorter growing seasons.
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In the northern U.S. and Canada, the growing season usually means the days between last and first frost, or approximately the last and first occurrence of 0° C (freezing) overnight low temperature. This is roughly May to October.
In much of Europe, the growing season is defined as the average number of days a year with a 24-hour average temperature of at least 5 °C (6 °C is sometimes used). This is typically from April until October or November, although this varies considerably with latitude and altitude.
In the United Kingdom, the growing season is defined as starting when the temperature on five consecutive days exceeds 5 °C, and ends after five consecutive days of temperatures below 5 °C. The 1961 to 1990 average season length was 252 days (8.4 months).
In some warm climates (like in the subtropical Savanna), the growing season is limited by the availability of water, with little growth in the dry season.