Last updated: November 25, 2025
Article
Climate Monitoring at Tonto National Monument: Water Year 2024
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Overview
Together, climate and hydrology shape ecosystems and the services they provide, particularly in arid and semi-arid ecosystems. Understanding changes in climate and water is key to assessing the condition of park natural resources—and often, cultural resources.
At Tonto National Monument (Figure 1), Sonoran Desert 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 resource problems, allowing managers to mitigate them before they become worse. At Tonto National Monument, we monitor climate, among other vital signs.
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 presents the results of climate monitoring at Tonto National Monument in WY2024.
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Climate and Weather
There is often confusion over the terms, “weather” and “climate.” Weather describes short-term 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 (Roosevelt 1 S #027281) had been operational three miles (4.8 km) from Tonto National Monument since 1905. In 2019, this station was relocated to Tonto National Monument (Figure 1). Because of this geographical move, current weather data from this station are no longer directly comparable to the long-term climate dataset. As a substitute, climate analyses in this year’s report use 30-year averages (1991–2020) of gridded surface meteorological (GRIDMET) data from the location of the station.
GRIDMET is a spatial climate dataset at a 4-kilometer resolution that is interpolated using weather station data, topography, and other observational and modeled land-surface data. Temperature and precipitation estimated from GRIDMET may vary from actual weather at a particular location, depending on the availability of weather station data and the difference in elevation between the location and that assigned to a grid cell. Data from both the weather station and GRIDMET are accessible through Climate Analyzer.
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Results
Precipitation
Highlight: A wet winter and relatively dry monsoon season resulted in near average annual precipitation.
Annual precipitation at Tonto National Monument in WY2024 was 13.15″ (33.4 cm), 0.34″ (0.9 cm) less than the 1991–2020 annual average. Overall, the cool season months (October–March) in WY2024 received 1.77″ (4.5 cm) more precipitation than the 1991–2020 average, primarily coming in February and March, which were more than twice as wet as the monthly averages (Figure 2). The warm season (April–September) was drier than average by 2.11″ (5.4 cm), primarily because of a much weaker than average monsoon season (June–September).
Air Temperature
Highlight: Temperatures were similar to the 30-year averages.
The mean annual maximum temperature at Tonto National Monument in WY2024 was 82.8°F (28.2°C), 0.2°F (0.1°C) above the 1991–2020 average. The mean annual minimum temperature in WY2024 was 58.3°F (14.6°C), 2.5°F (1.4°C) above the 1991–2020 average. Mean monthly maximum and minimum temperatures WY2024 differed by as much as 6.8°F (3.8°C; see November as an example) relative to the 1991–2020 monthly averages (Figure 2). Mean monthly maximum temperatures were cooler than average in January–May and warmer than average in all other months. Mean minimum temperatures were warmer than average in all months except March and April.
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Drought
Highlight: Mild drought conditions followed a wetter 2023.
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 Tonto National Monument indicates that WY2024 was similar to 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
Author: Kara Raymond
Raymond, K. 2025. Climate Monitoring at Tonto National Monument: Water Year 2024. Sonoran Desert Network, National Park Service, Tucson, Arizona.