Seasonal unemployment refers to unemployment that exists on a set schedule within certain industries as a result of fluctuations of the weather and seasons. It is an expected type of unemployment that is part of the natural course of doing business, as distinct from unemployment caused by business losses, slow growth of the economy or recession. When a government reports unemployment rates, those rates are adjusted to account for the phenomenon of seasonal unemployment in order to give an accurate picture of the true amount of people without jobs in the economy.

Seasonal unemployment, also referred to as periodic employment, exists in any field or industry that is dependent upon the weather. For example, most road construction projects take place in the summer and most new properties or homes are built during the summer so, as a result, construction workers or contractors may be laid off each winter and hired back each spring when construction begins again; this is a form of seasonal unemployment. Seasonal unemployment can also occur in tourist industries and resort towns; if, for example, a town only receives visitors during a particular season and then experiences an "off season" in which no one visits, the hotels and other tourist-related services may lay off employees during that off season.

Those individuals who work in seasonal jobs traditionally are laid off, which means they are invited to return again during the on season. After being laid off, many seasonal employees have a second job they do during the months when they cannot work in their seasonal job. Others collect unemployment benefits during the off season to survive until the seasonal job begins again.

Because seasonal employment is an expected and normal part of doing business within given industries, the government does not want to consider those who are unemployed as a result of seasonal shifts when it determines the percentage of individuals unemployed at any given time. Unemployment indexes created by the government are used as a measure of the success of the economy as a whole; high jobless numbers can indicate slow business growth and can adversely affect consumer confidence and the valuation of stocks on the stock market. Since seasonal employees have jobs and may not be looking for work during the off months, the unemployment figures are thus adjusted to discount these seasonal employees in determining the percentage of the population seeking work.