ABSTRAK. Penelitian ini bertujuan untuk menguji kontribusi faktor klimat di musim kemarau terhadap kondisi mikroklimat closed house periode brooder dengan panjang kandang berbeda. Unit kandang digunakan yaitu kandang ukuran panjang 60 m dan 120 m. Pengamatan dilakukan pagi hari (05.00 WIB), siang hari (13.00 WIB) dan malam hari (21.00 WIB). Parameter makroklimat yang diamati meliputi suhu, kelembaban udara, kecepatan angin dan radiasi matahari serta kondisi mikroklimat meliputi suhu, kelembaban udara, kecepatan angin dan THI. Besaran kontribusi diukur berdasarkan keeratan hubungan dengan analisis korelasi. Koefisien korelasi yang menunjukkan hubungan cukup kuat dengan nilai r0,3, digunakan untuk membentuk persamaan regresi. Hasil penelitian menunjukkan besaran kontribusi komponen makroklimat pada pagi hari, siang hari maupun malam hari terhadap kondisi mikroklimat berupa suhu, kecepatan angin dan THI lebih besar di kandang panjang 60 m, sedangkan kontribusi makroklimat terhadap kelembaban udara mikroklimat lebih besar di kandang 120 m (p0,05). Rentang nilai r pada korelasi yaitu cukup kuat hingga sangat kuat. Hasil persamaan regresi yang terbentuk memiliki nilai determinasi R2 sangat kuat, sehingga layak digunakan sebagai prediktor. Prediktor kelembaban udara di kandang 60 m berupa kecepatan angin, kelembaban udara dan radiasi matahari makroklimat, sementara prediktor kelembaban udara di kandang panjang 120 m berupa suhu, kelembaban udara dan radiasi matahari. Simpulan penelitian yaitu kontribusi faktor makroklimat terhadap variasi kondisi mikroklimat berupa suhu, kecepatan angin dan THI pada periode brooder lebih besar di kandang 60 m daripada 120 m, sedangkan kontribusi komponen makroklimat terhadap kelembaban udara di kandang 120 m lebih besar dari kandang 60 m. (Contribution of climatic factor outside the lengths to the change of microclimate closed house with different lengths in brooder period in the dry season) ABSTRACT. This study conducted to calculate macroclimate contribution during brooding period house to different closed house length in dry season. Two broiler closed house 60 m and 120 m length here used in this research. Observed data were daily at 05.00 a.m, 1.00 p.m. and 9.00 p.m to represented microclimate condition in the morning, afternoon and night. Macroclimate parameters observed included temperature, relative humidity, air velocity, sun radiation and microclimate parameters included temperature, relative humidity, air velocity, THI. Macroclimate contribution on the microclimate was calculates based on the strength of the relationship using correlation analysis. Subsequently, regression equation formed on parameters which has r value more than 0.3. Results showed that macroclimate contributes on variation of microclimate condition such as temperature, air velocity and THI which is larger in the 60 m length than 120 m length closed house(p0.05). Macroclimate factors contributes on microclimate humidity which is larger in the 120 m than 60 m closed house length. The range of correlation r value are strong enough to very strong. Regression equations confirmed to having strong determination R value, thus can be used as a predictor of microclimate variation. Predictor parameter of microclimate humidity in 60 m closed house consist of air velocity, relative humidity and sun radiation, whereas microclimate humidity in 120 m closed house predictors consist of temperature, relative humidity and sun radiation. In conclusion macroclimate that contributes to the microclimate variation consist of temperature, air velocity and THI, which is larger in 60 m than 120 m closed house. Meanwhile, macroclimate that contributes to the microclimate humidity is larger in 120 m than 60 m closed house.