Upper Trestles - surf spot statistics

Upper Trestles is a high-quality surf spot that benefits from consistent ground swell year-round, though the best conditions are typically found between April and October. During these months, ground swell dominates (90%+ of the time), with minimal wind swell interference, making for clean, well-organized waves. The mean swell size hovers around 0.8-0.9m, providing ideal conditions for performance surfing. However, wind conditions are often less favorable, with bad onshore winds occurring 60-75% of the time, peaking in May and June. The late summer and early fall months (September-October) offer slightly better wind conditions, with good winds around 38-39% of the time, improving wave quality despite the swell size tapering slightly. Winter months (November-March) see more variability, with increased wind swell and no-swell days, while ground swell remains strong but less reliable. December and January have the highest chance of no swell (25-31%) and the smallest average wave heights (0.7m). For the best balance of swell consistency and manageable wind conditions, September and October stand out, though dedicated surfers can find good waves from late spring through early fall if willing to work around the frequent onshore winds.

Upper Trestles in September typically offers clean, rippable conditions with a predominant SSW swell direction, which aligns well with the spot’s orientation. The average swell height of 0.8m combined with a long 15s period translates to consistent, well-shaped waves, often in the 1-1.5m range (making up ~7% of conditions, with 62% of swells falling in the 0.5-1m range). The swell energy is primarily from the SSW (70.5% of waves) and SW (21.99%), ensuring favorable angles for groomed peaks. Wind conditions are rideable 38% of the time, with the most common disruptive winds being light to moderate WSW (12.38% occurrence, often 10-20kph). Morning sessions frequently benefit from lighter winds, while afternoon sea breezes can occasionally texture the surface. Expect smaller but high-quality waves early in the month, with occasional larger pulses later in September. Advanced surfers will find the most potential when SW swells overlap with lighter E/NE offshore winds (combined probability ~3-5%). The spot’s consistency and shape make it reliable for performance surfing, though size limitations mean bigger days are rare.