Peru is located on the central part of western South America and is hemmed in by the Pacific Ocean. Home to more than 24 million inhabitants, the country covers a surface of 1,285,215 km2 (about the combined size of Spain, France and Italy) making it one of the 20 largest countries on Earth.

Also because of their geographical location, Peru’s coasts have traditionally served as a vital point in maritime and trade routes on the subcontinent. Moreover, Peru has sovereign rights over 200 miles off its coasts, and territorial rights over 60 million hectares in Antarctica.

The Coastline
Due to the presence of the cold Humboldt Current and the fact the coast is limited to the east by the Andes, the Coastline is a long barren desert where there is almost no rain. Winter runs from April to October in the central and south coastal regions while summer lasts from November to March.

In winter, skies are heavily overcast and a light drizzle, called garúa, is frequent. Despite an intense chill factor caused by high humidity, temperatures rarely fall below 12º C.

In Summer, however, the sun shines brightly, making temperatures frequently rise to 30º C. The north coast is not affected by cold water currents, which is why the area is blessed with almost 300 warm, sunny days a year with temperatures that can reach 35º C in summer. The El Niño weather phenomenon considerably increases rainfall in this region from November to March.

The Andes
Two distinct seasons can be found in the Andes. One is a rainless winter that runs from April to October when days are sunny and nights cold with frequent frosts, thus making it the perfect time for a visit. Heavy rains (generally more than 1,000 mm or about 40 inches), fall in the rainy season –erroneously known as "winter"– that lasts from November to March.

The Andean climate features radical temperature changes over the same 24-hour period from 24º C in the day to as low as 3º C at night. The mountain climate is dry and favors a wide variety of crops.

The Jungle
Split into the high jungle (above 700 masl) and low jungle (below 700 masl). The subtropical, mild climate of the high jungle features rainfall (approximately 3,000 mm or 120 inches a year) from November to March and sunny days from April to October. Nights are always cool.

In the lower jungle or Amazon plain, two well-marked seasons are directly related to distance to the Equator. In the dry, travel season running from April to October, days are often sunny and temperatures climb above 35º C. River flow drops and roads are usually open to traffic. From November to March, showers are frequent –at least once a day– and road travel difficult.

Humidity is extremely high throughout the year. From May to August, an occasional frost originating in cold fronts, called friajes or surazos, blowing north from the southern tip of the subcontinent may hit the southern jungle and make temperatures fall to between 8 and 12º C.

It is often said that in tropical mountain ranges, rather than four seasons in the year, there are four seasons in a day. Mornings in the Peruvian Andes are bright but cool like in springtime.

The day heats up through noon when, like in summer, many head for the shade. In the afternoon, cumulus clouds that appeared in the sky during the morning hours reach their climax, and the oblique rays of the sun make it feel like autumn. After the usually short sunset, a winter cold sets in.

Such varied weather patterns result from the location of the Andes, which run from north to south and separate the warm and humid Amazon basin winds from the masses of cold wind blowing from the Pacific Ocean.

Due to their tropical location, the Peruvian Andes feature well-defined rainy and dry seasons with an almost imperceptible transition period between the two.

Also, due to Peru’s location in the Southern Hemisphere, seasons are reversed compared to Europe and the United States.

May to September
Winter or the dry season is the only season open to high mountain climbing. Proximity to the Equator means shorter days by 30 to 50 minutes as the season moves on. Frosts occur above 4,500 masl. July offers the best weather, before the cold northern winds start blowing in August.

September to December
A season suitable for climbing lower glaciers and trekking, it is similar to spring in the Northern Hemisphere. Afternoon showers and an occasional electric storm become more frequent as cumulus clouds dump off their morning humidity in a matter of minutes. Skies are then clear before night falls and the skies become studded with stars.

December to May
A season of torrential afternoon storms, and occasional light, persistent drizzle, this is not an appropriate time for mountaineering expeditions in the Andes. On a rainless day, a walking tour may be possible along a gully, although streams, almost dry in winter, can become impossible to cross during this time of the year.

Always check with the local residents about the state of repair and condition of roads. However, they should not be relied upon to provide accurate information on time and distance since their replies are based on subjective impressions. The usual "just over the hill" answer usually implies long hours of strenuous uphill climbing at great altitude.

“Leave nothing but foot prints, take nothing but pictures.” Plants must not be uprooted or cut. Do not start fires in high altitude forests. Do not deface road signs. Fishing and hunting are forbidden in the dry season (when trout fishing is strictly banned).

Always tell local authorities or the mountaineers’ association when you are entering a mountain area.

Never trek or climb by yourself. Do not litter. Bring back all disposable materials and wastes. Leaving them on the mountain trail causes pollution

Andean mountains are also subject to global warming and glacial retrenchment which translates into the loss of about two meters (6 ft.) of snow every year with the ensuing ongoing changes of aspect and feasible approaches to the mountains. Large masses of serac or compacted snow blocks break off. Above 4,500 masl, rain falls as snow.

Generally, snow in the Andes sticks firmly to steep slopes and may even form shelves near the leeward side of the summit. Exceptionally, shelves may appear on both sides of a ridge. Another peculiarity of mountains in this region is the appearance of stepped or grooved snow walls.

Mountain faces in the Southern Hemisphere have a number of features that make them different from those in the Northern Hemisphere.

North faces are sunnier. The sun and cold modify snow and ice. The best climbing snow can be found here.

South faces are more stable. Snow remains unchanged due to scarce sunlight and temperatures usually drop below 0º C. Plenty of soft snow is found at the beginning of the dry season from May to September.

East and West faces show mixed features. Quite often, a hike along a west- or east-oriented shelf will reveal substantial changes in snow conditions.

There are practically no high mountain shelters in Peru except in the Cordillera Blanca which features a single, well-prepared shelter at the end of the approach to the Pisco glacier. There are also shelters near the Parón lagoon in Ancash owned by a hydro-electric power station and another on the ascent route to the Misti (Eagle’s Nest) volcano in Arequipa.

These must be trusted to highly trained guides. In the Cordillera Blanca and Huayhuash areas, rescue efforts are coordinated by the Guides’ Association (Casa de Guías), which should be contacted to carry out search and rescue missions. The victims or their relatives must pay the corresponding expenses. When helicopter support is needed, the respective consular authorities will negotiate rental fees with the Peruvian Navy or Air Force. Total rescue expenses usually fluctuate between US$3,000 and 5,000.

Generally the UIAA scale is used to rate the ascent’s degree of steepness and difficulty whether on rock, snow or ice.

Easy (E): snow slopes up to 40º.

Slightly difficult (SD): snow slopes up to 45º with an occasional harder short segment. Mixed or rock to degree II.

Moderately difficult (MD): snow slopes up to 45º with an occasional harder, somewhat longer segment. Mixed or rock to degree III.

Difficult (D): slopes up to 55º on snow with one or two long ice segments between 60º and 70º, or shorter but harder segments. Mixed or rock up to degree IV.

Very difficult (VD): numerous long, sustained segments at 60º on ice and one or two long ice passages between 70º and 85º or shorter somewhat harder passages. Mixed or rock to degree V.

Extremely difficult (ED): long vertical passages on ice. Mixed or rock to degreee VI and occasional artificial surface.

Exceptionally difficult (XD): long haul itinerary of degree VII mountaineering difficulty, involving long, sustained and exposed passages.

All mountain work, whether permanent or temporary is subject to an official and professional classification. All mountain personnel must have an ID card issued by the Ministry of Tourism, the respective national park (as in the Huascarán National Park) or the Huaraz Guides’ Association.

Mountain guides: either working in teams or freelancing, all mountain guides have received certified training. Experienced and trained to climb the main snow-capped mountains.

Trekking Guides: Not necessarily trained as mountain climbers, they are nevertheless familiar with the walking routes and circuits. They usually travel with large expeditions organized by tour operators.

Mountain Guide Trainees: After completing their training, mountain guides go through a year’s trial period during which they are officially not allowed to guide certain difficult ascents.

First class porters: They assist mountain climbers wherever beasts of burden cannot reach. Not allowed to climb above 6,000 meters. Usually they are fully equipped, and are capable of overcoming extremely adverse obstacles and conditions. However, climbers must provide them with the required high mountain gear.

Second class porters: They assist mountain climbers and trekkers in areas not accessible to pack animals but will not go into snow areas.
Mule drivers: In heavy demand among climbers, they own the beasts and usually live near the most popular mountains or routes. Mule drivers must be licensed. A community-enforced rule allows them to work only near their towns. Drivers must be paid for the time spent returning to their towns and for their food.

Cooks: Certified cooks are valuable members of any expedition. Cooking is no simple task above 4,000 meters of altitude. Generally they assist in buying groceries and many also have the necessary cooking ware and utensils. Cooks are also responsible for guarding the camp while travelers are away.