Eugene Weather

This page contains information on Eugene weather, and is intended for the use of participants in conferences at the Department of Mathematics at the University of Oregon. More data about the climate in Oregon, as well as links to current weather forecasts, road conditions, ski reports, and more, is available from the Oregon Climate Service (badly designed page: puts text under pictures and under other text unless JavaScript is turned on). The National Oceanic and Atmospheric Administration provides current Eugene weather forecasts online. You can find other weather information starting there.

Eugene is normally warm and very dry in the summer, and cool (but usually above freezing) and damp in the winter. The following is from the 1993 "Local Climatological Data" for Eugene, published by the National Oceanic and Atmospheric Administration:

The first fall rains usually arrive during the second or third week of September, after which rain gradually increases until about the first of January and then slowly decreases to the latter part of June. July and August are normally very dry, occasionally passing without rainfall. When snow occurs, it frequently melts on contact with the ground or within a few hours, but occasionally an accumulation of a few inches will persist as a ground covering for several days. Snowfall for a winter season exceeds 5 inches in about one-third of the years.
Temperatures are so largely controlled by maritime air from the Pacific that long periods of extremely hot or severely cold weather never occur. Temperatures of 95 degrees [Fahrenheit] or higher have occurred only in the months of June, July, August, and September, and average three days a year.

The table below, based on the same source, gives normal high and low temperatures (in degrees Fahrenheit) and average monthly precipitation and snowfall (in inches) based on the 30 year period ending in December 1993. The letter T under snowfall indicates that a trace of snow was recorded during that month in at least one of the years of the period. Note that evenings are generally cool during the summer even when the days are not. Also, the daily variation in temperature is usually much less during the winter than during the summer.

Month:  Jan.  Feb.  Mar.  Apr.  May   June  July  Aug.  Sep.  Oct.  Nov.  Dec.
High:   46.4  51.4  55.9  60.5  67.1  74.2  81.7  81.8  76.2  64.6  52.4  46.2
Low:    35.2  37.0  38.9  40.6  44.5  49.7  52.8  53.2  49.3  43.5  39.7  35.9
Rain:   7.91  5.64  5.52  3.11  2.16  1.43  0.51  1.08  1.67  3.41  8.32  8.61
Snow:    3.7   0.8   0.5    T     T     T     0     0     T     T    0.3   1.3

During the same 30 year period, there have been 8 years with at most 0.1 inch of rain during July, 11 years with at most 0.1 inch of rain during August, and 5 years with at most 0.1 inch of rain during September. In one year, there was no rain at all during July and August combined, and in two others only a trace.

This table conceals some significant variations. During the summer, it is common for periods of hot clear days to alternate with periods of cool days with low cloud during part (occasionally all) of the day and occasional drizzle. Highs close to or above 90 are common; so are highs around 70. Usually there will be at least one very hot spell during the summer, with temperatures close to or over 100. Temperatures below 40 have been recorded in all months of the year, and 32 or below in all months except July and August.

During the winter, clear skies are quite rare, but periods of fairly dry weather with intermittent drizzle alternate with storms (usually not very windy in Eugene) bringing an inch or two of rain per day and lasting several days. Most winters there will be a short period of clear and cold weather, with lows below 15. Temperatures below 0 have been recorded in December, January, and February. There are also warm spells, during which the ski areas get rain instead of snow.

Exactly when the real rains occur is also quite variable. During the 30 year period of the table, the rainfall in November has varied from 1.33 to 20.48 inches, in December from 1.24 to 20.99 inches, in January from 0.31 to 15.09 inches, and in February from 0.86 to 14.22 inches. By contrast, total annual rainfall has varied only from 33.83 to 64.01 inches (with a mean of 46.41). One winter during this period there was about 4 feet of snow in January, and it stayed on the ground for over a month, but normally snow comes in amounts of 2 to 6 inches and stays around for two days to a week. Some winters there is no snow at all, and there is rarely significant snow more that twice in a winter.

The start of the rainy season can vary from sometime in August to late October, and its end can vary from sometime in May to late June. Spring and fall usually get a significant amount of clear weather along with the rain.