ヨセミテ国立公園 5月の天気

May is peak waterfall season in Yosemite Valley — the forum puts high water at roughly mid-May to mid-June, with the falls thundering rather than trickling by late May. The catch is elevation, and it is worth knowing that the park-wide averages shown here reflect the high country rather than the Valley floor: while the Valley is mild and green in May, Tioga Road and the high country are usually still under snow, typically opening late May or into June. Across the last thirty years the earliest opening was 29 April and the latest 1 July, and a late spring storm can close it again afterwards. Plan the Valley for May; plan Tuolumne for July.

Yosemite-forum threads on a March visit describe waterfall flow as genuinely still building toward the May snowmelt peak, posters naming this month strong but not yet at full volume. Regulars call valley-floor snow genuinely inconsistent given the roughly four-thousand-foot elevation, several posters naming a real chance of a spring storm and tire-chain requirements at higher elevations. Posters call Yosemite Falls genuinely viewable from most valley vantage points in March, several regulars naming this a reason the month still works well for waterfall viewing. Regulars call Tuolumne Meadows and Glacier Point genuinely closed this time of year, several threads naming this a real limitation for the high country. Posters recommend checking tire-chain requirements before a March trip, several regulars calling this standard given how unpredictable spring storms remain. The record: 0.9C days, -7.3C nights, an extraordinarily high 220mm across nearly 13 days and 74 percent humidity.

Yosemite National Park-forum threads on a September visit call this genuinely one of the better windows, posters describing considerably fewer crowds compared with peak summer while daytime conditions stay comfortable and dry. Regulars call high Sierra hiking a real September highlight, trails there noticeably less crowded than the main Valley routes even during one of the park's busier months overall. Posters call waterfall flow genuinely reduced by September, Vernal and Nevada Falls still holding some water while Yosemite Falls can run down to a thin trickle or even stop entirely. Regulars recommend planning around lower water levels rather than expecting a spring-style spectacle, September's appeal here resting more on hiking than waterfalls. Posters recommend booking well ahead regardless of the lighter crowds, September still ranking among the park's three busiest months. The record: 18.6C days feeling like 19C, 6.2C nights, 27.5mm across over 5 days and 42 percent humidity.

Yosemite-forum threads on how the park runs in February describe this as genuinely one of the best months for anyone comfortable with winter conditions, posters calling the valley considerably quieter than the summer crush. Regulars call chains mandatory for driving in this time of year, Tioga Road and Glacier Point Road both fully closed regardless of conditions elsewhere. Posters describe the YARTS bus from Mariposa or El Portal as a real alternative to driving, avoiding the chain requirement. Regulars call the famous Horsetail Fall 'firefall' effect a genuine highlight, the glow appearing only on clear evenings in the second half of the month when sunset light hits the water right. Posters recommend real layers and traction devices for valley floor walks, icy patches common on shaded trails. Regulars call the near-empty valley a genuine reward for the cold. The record: 0.3C days feeling like -3C, -8.5C nights, an extraordinarily high 202.7mm across 10 days and 68 percent humidity.

Yosemite-forum threads on July waterfalls are consistent the valley's falls are well past their spring peak by this point, Yosemite Falls typically the first to thin to a trickle, but posters call the flow entirely dependent on how much water built up in the high country the prior winter - a heavy winter can keep real water moving well into the month. Vernal and Nevada Falls, reached via the Mist Trail, are repeatedly named the best bet for still-flowing water in July regardless of the year. Days run warm enough for shorts and a t-shirt, evenings cool enough that a proper jacket is standing advice, and afternoon thunderstorms are common enough that ponchos are worth packing even under a clear morning sky. Regulars call July warm on the valley floor but genuinely pleasant once up on the higher trails. The record: 23.3C days feeling like 22C, 10.3C nights, just 16mm across 4.8 days, 42 percent humidity and 13.5 hours of sun.