We aimed to assess the performance of different methodologies to estimate the reference evapotranspiration (ET0) in different seasons for at 1, 3, 6 and 10 days for the Northwestern Mato Grosso do Sul. We used a set of daily data obtained from the networks of the Brazilian National Institute of Meteorology for Água Clara, Cassilândia, Chapadão do Sul, Paranaíba and Três Lagoas locations. The meteorological data used were: maximum and minimum air temperatures, wind speed, solar radiation, and

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... ative humidity. The methodologies used for the ET0 estimation were Hargreaves-Samani and Penman-Monteith (PM-FAO) using all the meteorological data needed and missing data on relative humidity, solar radiation and wind speed. To compare ET0 values estimated by means of equations tested against the PM-FAO method we analyzed the parameters of linear regression equation "β 0 " and "β 1 ", coefficient of determination (r²), standard-error of estimate (SEE) and coefficient of performance (c). The PM-FAO method with missing data (relative humidity and wind speed) were the best alternatives to estimate ET0, followed by the PM-FAO method with missing solar radiation data in all timescales during fall and winter seasons. The Hargreaves-Samani method is not recommended to be used in its original form to estimate ET0 in the Northwestern Mato Grosso do Sul, in none of the timescales and seasons.