Greeley experiences a semi-arid climate . High temperatures are generally around 90–95 °F (32 °C) in the summer and 40-45 °F (4 °C) in the winter, although significant variation occurs. The hottest days generally occur around the third week of July and the coldest in January. Nighttime lows are near 60 °F (16 °C) in the summer and around 15–20 °F (−9 °C) in the winter. Record high temperatures of 112 °F (44.4 °C) have been recorded, as have record low temperatures of –25 °F (–32 °C). The first freeze typically occurs around October 10 and the last can happen as late as May 4. Extratropical cyclones which disrupt the weather for the eastern two-thirds of the US often originate in or near Colorado, which means Greeley does not experience many fully developed storm systems. Warm fronts, sleet, and freezing rain are practically nonexistent here. In addition, the city’s proximity to the Rocky Mountains and lower elevation, compared to the mountains west of the city, result in less precipitation and fewer thunderstorms. This is paradoxical, because adjacent areas (mostly farmland) experience between 7 and 9 hail days per year.
The climate in Greeley, as well as all of Colorado, is extremely dry. The Chinook winds coming off the mountains often raise temperatures to near 70 °F (21 °C) in January and February, and sometimes to near 90 °F (32 °C) in April. Greeley’s elevation and low year-round humidity means that nighttime low temperatures are practically never above 68 °F (20 °C), even in the hottest part of the summer. The diurnal temperature range is usually rather wide, with a 50-degree (Fahrenheit) difference between daytime highs and nighttime lows not uncommon, especially in the spring and fall. Rapid day-to-day and diurnal fluctuation in temperature is also common.