Crater Lake National Park, lying at Lat. 43 W. Long. 122 W., is near the mid-point of the Sierra-Cascade Mountain Province of the Pacific Mountain System (Raiz 1957). The climate is characterized by cool summers and moist winters with heavy snowfall. At all elevations within the Park freezing temperatures may occur any month of the year. Traces of snow have been observed in July. The 27 year record at Headquarters has recorded a -18° F. low, and a 91 F. high. Special attention is given to weather conditions during July and August, as these are the months during which land use (or occupancy) was most likely. The figures for both Park Headquarters and Chemult are given in Table 1 are taken from Sternes’ copilations (1965: Table I). These readings give the range of weather conditions one may expect at any elevation within the Park during the two months.
An interesting peculiarity of the Park is the occurrence of colder minimums at the lower elevations in the eastern part of the Park. Sternes (1963:5) states that these conditions are the result of three primary conditions: the formation of stagnant pools of cold air; the invasion of Arctic air from the northeast; the warming effects of marine air at higher elevations.
Table 1 . Climatological sumamry for the months of July and August recorded at Park Headquarters and Chemult
|Crater Lake National Park, 1924- 1961 July – August|
|Mean daily maximum temperature (F)||49.6||70.4||70.3|
|Mean daily mnimum temperature (F)||28.3||42.2||41. 6|
|Mean monthly temperature (F)||39.0||56.3||56|
|mean snow and sleet. (inches)||578.5||Trace||0.02|
|mean number of days with precip of 0.10′ or more||110||2||1|
|Chemult, 1937 -1961 Year July – August|
|Mean daily maximum temperature (F)||58.4||82.8||80.6|
|Mean daily minimum temperature (F)||24.7||36.5||33.8|
|Mean monthly temperature (F)||41.6||59.7||57.2|
|Mean precipitation (inches)||26.26||0.58||0.56|
|Mean snow and sleet (inches)||162.7||0||0|
|Mean number of days with precip. 0.10 or more||66||1||1|
There is a greater variation of the average annual totals of precipitation in the different parts of Crater Lake National Park than there is in the entire northeastern quarter of the United States. The most rapid change takes place down the eastern slope of the Park. Here the average yearly total declines from over 65 inches at the crest to slightly more than 25 inches at the Park’s lower edge. This sharp drop-off is due to the movement of practically all storms from the west. The large air masses they embody are cooled in ascending the western slopes of the Cascades, and much of their moisture precipitates out as a result. This leaves them with less moisture available for precipitation as they continue eastward down the other side of the mountain range. Also, as air moves to lower elevations its temperatures normally increase. Thus as it moves down these slopes rather than being in a condition of having to give up moisture it is steadily increasing its ability to retain it (Sternes 1963:6).