The San Juan's are actually the remaining mountain-tops of a receding continent much older than the American mainland. The islands are generally quite hilly, the tallest mountain being Mount Constitution at almost exactly a half-mile elevation, with some flat areas and valleys in between. The coastlines are a mixed bag of sandy and rocky beaches, shallow and deep harbors, calm and reef-studded bays. Gnarled, ochre-colored madrona trees stand along much of the cliffs overlooking the beaches while evergreen fir and pine forests cover large inland areas.
The San Juan Islands get much less rainfall than
Seattle because of protective shadowing from U.S and Canadian
mountain ranges. Summertime high temperatures are around 70 degrees
fahrenheit while average wintertime lows are in the high thirties and
low forties. Snow is infrequent in winter except for the higher
elevations. However, the islands are subject to high winds at times.
Those from the northeast sometimes bringing brief periods of freezing
and artic- like windchills.