Last updated: August 26, 2025
Article
Climate Monitoring at Bent's Old Fort National Historic Site: Water Year 2024
NPS/STUART WEST
Overview
Together, climate and hydrology shape ecosystems and the services they provide, particularly in arid and semi-arid ecosystems and across the Southern Plains (Woodhouse and Overpeck 1998). Understanding changes in climate, groundwater, and surface water is key to assessing the condition of park natural resources—and often, cultural resources.
At Bent’s Old Fort National Historic Site (Figure 1), Southern Plains Inventory and Monitoring Network scientists study how ecosystems may be changing by taking measurements of key resources, or “vital signs,” year after year—much as a doctor keeps track of a patient’s vital signs. This long-term ecological monitoring provides early warning of potential problems, allowing managers to mitigate them before they become worse. We monitor climate, among other vital signs at the park.
Climate reporting is by water year (WY), which begins in October of the previous calendar year and goes through September of the water year (e.g., WY2024 runs from October 2023 through September 2024). This web report the results of climate monitoring at Bent’s Old Fort National Historic Site in WY2024.
Reference: Woodhouse, C. A., and J. T. Overpeck. 1998. 2000 years of drought variability in the central United States. Bulletin of the American Meteorological Society 79(12): 2693–2714. https://doi.org/10.1175/1520-0477(1998)079%3C2693:YODVIT%3E2.0.CO;2.
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Climate and Weather
There is often confusion over the terms “weather” and “climate.” In short, weather describes instantaneous meteorological conditions (e.g., it’s currently raining or snowing, it’s a hot or frigid day), and climate reflects patterns of weather at a given place over longer periods of time (seasons to years). Climate is the primary driver of ecological processes on earth. Climate and weather information provide context for understanding the status or condition of other park resources.
Methods
A National Oceanic and Atmospheric Administration Cooperative Observer Program (NOAA COOP) weather station (La Junta Colorado Municipal Airport #54720) is located 4.2 miles (6.7 km) west of Bent’s Old Fort National Historic Site and has been operational since 1945 (Figure 1). This station provides a reliable, long-term climate dataset used for analyses in this climate report. Data from this station are accessible through Climate Analyzer.
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Results
Precipitation
Annual precipitation near Bent’s Old Fort National Historic Site in WY2024 was 10.06″ (25.6 cm), 1.28″ (3.3 cm) less than the 1991–2020 annual average. WY2024 precipitation totals in the cool season months (October–March) were slightly below the 1991–2020 averages (Figure 2). No precipitation was registered at the weather station in October and November 2023. The remaining cool season months in WY2024 received above average precipitation. Notably, February was over four times wetter than average. Overall, the warm season (April–September) was drier than average. June and July both were approximately 50% wetter than average, but the other months received only a fraction (range of 14–56%) of their average precipitation. Extreme daily rainfall events (≥ 1.00″, 2.54 cm) occurred on 3 days, one more than the average annual frequency of 1.8 days. Extreme rainfall events occurred on 08 June 2024 (1.24″, 3.1 cm), 07 July 2024 (1.13″, 2.9 cm), and 16 July 2024 (1.41″, 3.6 cm).
Air Temperature
The mean annual maximum temperature near Bent’s Old Fort National Historic Site in WY2024 was 72.1°F (22.3°C), 2.1°F (1.2°C) above the 1991–2020 average. The mean annual minimum temperature in WY2024 was 39.8°F (4.3°C), 0.2°F (0.1°C) above the 1991–2020 average. Mean monthly maximum and minimum temperatures in WY2024 differed by as much as 5.4°F (3.0°C; see December as an example) relative to the 1991–2020 monthly averages (Figure 2). Mean monthly maximum temperatures were warmer than average in every month except January, March, and July. Mean monthly minimum temperatures were slightly cooler than average in every month except December, February, June, and August. Extremely hot temperatures (≥ 99.0°F, 37.2°C) occurred on 27 days in WY2024, four more than the average frequency of 23.2 days. Extremely cold temperatures (≤ 11.0°F, −11.7°C) occurred on 13 days, five less than the average frequency of 17.9 days.
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Drought
Reconnaissance drought index (Tsakiris and Vangelis 2005) provides a measure of drought severity and extent relative to the long-term climate. It is based on the ratio of average precipitation to average potential evapotranspiration (the amount of water loss that would occur from evaporation and plant transpiration if the water supply was unlimited) over short periods of time (seasons to years). The reconnaissance drought index for Bent’s Old Fort National Historic Site indicates that WY2024 was drier than the 1991–2024 average from the perspective of both precipitation and potential evapotranspiration (Figure 3).
Reference: Tsakiris G., and H. Vangelis. 2005. Establishing a drought index incorporating evapotranspiration. European Water 9: 3–11.
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Report Citation
Authors: Kara Raymond, Andy Ray
Raymond, K., and A. Ray. 2025. Climate Monitoring at Bent's Old Fort National Historic Site: Water Year 2024. Southern Plains Network, National Park Service, Pecos, New Mexico.