Weather, Physical & Biological Data

At 39° 00'N latitude and 123° 4'W longitude, HREC has a total area of 5,358 acres ranging in elevation from 500 to 3,000 feet (refer to topographical map). The climate is Mediterranean with hot, dry summers (June through September) and mild, rainy winters. Rainfall normally occurs between October and May, with 75 percent of the precipitation received from November through February. Annual precipitation averages 37 inches at the 800-foot level and 45 inches at 3,000 feet. Snow at the higher elevations is infrequent, generally not lasting more than a few days. Mean average temperature in July through September is 70° F, and the mean maximum is 92° F. July is generally the hottest month, with daily maximums sometimes reaching 110° F. Coastal winds and lack of cloud cover usually cause cool nights. Temperatures drop to a mean of 44° to 47° F from December through February. The frost-free growing season averages 250 days, with the first frost sufficient to cause soil heaving usually occurring in mid-November. Rainfall influences herbaceous forage growth more than temperature does, limiting the growing season to about 180 days (November through April).

The Center has been part of the National Atmospheric Deposition Program since 1979. This is a nationwide network of precipitation chemistry monitoring sites, and HREC's collector is located in the lysimeter facility. Concentrations and deposition of the major cations and anions in precipitation at Hopland from present back to 1979 are available to researchers.

Current Forecasts for the Hopland Area

• Yahoo Weather
• The Weather Channel

The Weather Stations

There are five weather stations located at the Hopland Research and Extension Center. These stations are arranged along an elevational gradient from the Russian River valley floor to the top of the Center at the boundary with the BLM Cow Mountain Recreational Area. Three of the stations are operated by the Center, and two by the State of California Department of Water Resources as part of the California Irrigation Management Information System (CIMIS).

Coon Lake

1500' elevation; monitored from 10/52; not computer compatible. Parameters measured before 9/89:

• precipitation with standard and recording rain gauges
• air temperature and humidity with hygrothermograph at 48" (weekly strip chart recorders)

Parameters Measured Since 9/89

• precipitation
• air temperature at 48"
• wet bulb, dry bulb and black globe at 72"
• soil temperature at 6" (weekly strip chart recorders)

Orchard

2900' elevation; monitored from 10/52; not computer compatible. Parameters measured:

• precipitation with standard and recording rain gauges
• air temperature and humidity with hygrothermograph at 48" (weekly strip chart recorders)

Headquarters

800' elevation; monitored from 10/52 to present; computer compatible from 7/79. Parameters measured:

• daily max/min air temperature at 48" with mercury thermometers
• precipitation with standard Weather Bureau collector

Weather station data summarized by month:

• Mean Minimum Temperature
• Mean Maximum Temperature
• Total Precipitation

Niderost (CIMIS #106 - Sanel, access data below)

500' elevation; monitored from 2/91 as part of CIMIS; computer compatible. Parameters measured:

• total solar radiation
• soil temperature air temperature/relative humidity wind direction and speed
• precipitation

Lambing (CIMIS #85 - Hopland, access data below)

1100' elevation; monitored from 6/60, and from 9/89 as part of CIMIS; computer compatible since 9/89. Parameters measured before 9/89:

• precipitation
• air temperature at 48"
• wet bulb, dry bulb and black globe at 72"
• soil temperature at 6"
• wind speed with anemometer at 72" and direction at 15' (weekly strip chart recorders)

Parameters measured since 9/89 (see #1 above).