Site Climate: Frost, Temperature, and Daylight

Companion to the rain and snowmelt harvesting plan, the 2027 planting plan, and the site baselines page (snow, storms, heat and chill, wind, sun, building values, and hail). The numbers live in data/climate.json and the SQLite tables built from it, so they can be queried and corrected. The lot has no weather station of its own yet, so these are the nearest measured record and two models, not readings on the ground (see How Well the Sources Agree).

Frost and Cold Log

The lot has no thermometer record yet. A minimum thermometer at tree height, plus one in the low northwest corner by the road, read each morning from March through October, would show how the orchard really compares with the station. Note when each tree type blooms, so the date can be checked against the risk tables.

Sources and Method

• USDA NRCS National Water and Climate Center, Prairie SNOTEL, site 704 (Elmore County, 4,800 ft, 43.505° N, 115.573° W): daily minimum and maximum air temperature, 1988 to 2026. This is the measured record behind every frost date, monthly average, and coldest night above.
• NOAA Regional Climate Centers, ACIS web services: the SNOTEL record, the old Prairie weather station (NOAA cooperative observer 107327, 1925 to 1942, cooperative observer network), and the PRISM grid, all retrieved October 18, 2026.
• PRISM Climate Group, Oregon State University: daily minimum and maximum temperature on a 4 km grid, sampled in the cell around the lot (43.458° N, 115.583° W, 4,688 ft). A model, not a measurement.
• Daymet, Oak Ridge National Laboratory: daily temperature on a 1 km grid (Thornton, Shrestha, Wei, Thornton, Kao, and Wilson, 2022, Daymet version 4 R1, doi:10.3334/ORNLDAAC/2129), sampled at the lot center. A model, not a measurement.
• USDA NRCS Web Soil Survey report for the property (soil folder): frost-free period of 60 to 100 days for map unit 149, Simonton loam, 2 to 12 percent slopes.
• Utah State University Extension, Critical Temperatures for Frost Damage on Fruit Trees (IPM-012-11, 2020): the blossom-kill temperatures above. UC IPM, Bacterial Canker (cherry): the disease is worse after spring freezes.
• USDA Plant Hardiness Zone Map (2023 edition, built by the PRISM Group at Oregon State University, data and terms): the 5 °F half-zone bands used to turn the average coldest night into a zone. The official grid was also read for the lot's own cell on October 18, 2026; the result is under Still to Check. The zones in the tables above are worked out from the readings, so they can differ from the map's answer.
• Daylight: the NOAA solar position formulas (Meeus, Astronomical Algorithms) at the lot's latitude and longitude, with sunrise and sunset at the sun's upper edge after standard refraction over a flat horizon. Checked against the U.S. Naval Observatory sunrise and sunset service for 12 dates, all within one minute. Hills, trees, and the windbreak shorten the direct sun on the ground.
• Method: the last spring freeze is the last day from January 1 to July 31 whose lowest temperature was at or below the threshold, and the first fall freeze is the first such day from August 1 to December 31. Percentiles are interpolated across the years from 1991 to 2020 with usable records (the year-by-year dates are in data/climate.json). A year's spring or fall date is left out when a missing day could be hiding a later or earlier freeze: the SNOTEL record has too many gaps in 1989 to 1993 and 2022 to date both freezes. Daily values come from hourly readings, so they can miss the coldest moment.