Some of the worlds worst weather can be found on this mountain. Extreme climate, harsh wind and snow, and unbearable cold can be expected when climbing Mount Washington. The highest temp in the summer ever recorded was only in the mid-high 70s. It can snow here in August, rain ice in winter or spring, or have winds above 200 mph! The highest wind ever recorded on earth was on top this mountain at 230+ mph. Aside of these interesting factoids there is a lot of climbing on this mountain. Tuckermans Ravine, Huntington Ravine, Raymond Cataract, and many other places like Gulf of Slides offer steep ice and snow. This area is a known training grounds for climbers wishing to get serious wind and cold exposure. Just the hike to the summit in summer is a thrilling and fun experience (with much better weather of course).
Bring cold weather gear year round. You can get snow even in summer. Summer can be really pleasant to climb but will probably be a bit chilly up on the rock. Steep snow routes can be found all over the mountain. Tuckermans and Huntington are the most favored. Gulf of Slides and Raymond Cataract are good too but farther approaches. For rock, Huntington is the most popular and there is a small amount in Tuckermans. You can also find some high alpine bouldering in Tucks as well but it is a bit limited. There is some remote bouldering in Huntington too.
This can vary greatly. A standard alpine rack for technical rock. Ice gear can vary too, you may need snow pickets for certain climbs. If you are just hiking I would look at weather and take a waterproof shell and a warm layer. A helmet for rock routes is a must. Most climbing is a 2 mile approach so bring plenty of water and high energy snacks.
Most of the climbing is accessable from the Pinkham Notch parking lot. There is a great visitors center with maps, topos and much more there. We highly recommend stopping there and getting bearings before attempting any climbs. There is also a climbers register. Get there early in the day as it can become infested with tourists.
View the topos and beta for Huntington Ravine, the most popular part of Mount Washington to climb at.