The climate in Papua New Guinea is hot and humid throughout the year along the coasts and in the plains, while it progressively becomes cooler, and then colder, as you go up in altitude. In much of the country, covered with dense rainforests, there is no dry season, so we can speak of equatorial climate, while in some inland valleys and along the south coast, there is a relatively dry season from July to September, and therefore the climate is tropical.
The climate is influenced by the monsoon circulation, the northwest monsoon from December to April, and the southeast monsoon from May to October, which usually bring rainfall in the exposed slopes, but in many areas even in both of them.
Rainfall typically varies from 2,000 to 4,000 millimetres (80 to 160 inches) per year, with some higher peaks on the exposed slopes, where it reaches as high as 7/8 metres (23/26 feet) per year, while it drops to 1,000/1,500 mm (40/60 in) in the southern coast, overlooking the Gulf of Papua and the Coral Sea.



In Madang, on the north-eastern coast of New Guinea, 3,500 mm (138 in) of rain per year fall, with a maximum of 430 mm (17 in) in April and a minimum of 120 mm (4.7 in) in August, so we are in the area that has an equatorial climate. Here is the average precipitation.
Average precipitation - Madang

Madang	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Madang	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	305	300	380	430	385	275	195	120	145	255	340	370	3500
Prec.(in)	12	11.8	15	16.9	15.2	10.8	7.7	4.7	5.7	10	13.4	14.6	137.8
Days	17	16	19	18	17	11	11	9	10	11	13	18	170

East of the mainland, the islands (including New Ireland, New Britain and Bougainville) are very rainy throughout the year as well. In general, the rains are most abundant from December to April, but not everywhere: in Lae, facing south-east in the Huon Gulf, the rains are most abundant in July and August, when more than 500 mm (20 in) per month fall.
On the coasts, the temperatures are high and stable throughout the year in the north, around 30 °C (86 °F) during the day, while in the south, located farther from the Equator, they decrease a bit in the period that can be called winter, from June to September.
Here are the average temperatures of Madang.
Average temperatures - Madang

Madang	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Madang	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	23	23	23	23	23	22	22	22	22	22	23	23
Max (°C)	30	30	30	30	30	30	29	29	30	30	30	30
Min (°F)	73	73	73	73	73	72	72	72	72	72	73	73
Max (°F)	86	86	86	86	86	86	84	84	86	86	86	86

The amount of sunshine on the coasts is generally decent, but not exceptional, however it is a little higher from May to October. Here are the sunshine hours in Madang.
Sunshine - Madang

Madang	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Madang	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	5	5	5	5	7	7	7	7	7	7	6	5

The capital Port Moresby is located in the southern area, which as mentioned is less rainy and more sheltered, so much so that it receives only 1,000 mm (40 in) of rain per year, with a relatively dry period from May to November, when rainfall drops below 70 mm (2.8 in) per month; in particular, the rains are scarce from June to October. Here is the average precipitation.
Average precipitation - Port Moresby

Port Moresby	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Port Moresby	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	180	195	170	105	65	35	30	18	25	35	50	110	1018
Prec.(in)	7.1	7.7	6.7	4.1	2.6	1.4	1.2	0.7	1	1.4	2	4.3	40.1
Days	9	8	10	6	3	4	3	2	2	3	4	7	61

In the capital the best period is the one that runs from June to September, because it is also, albeit slightly, the least hot, with maximum temperatures around 29/30 °C (84/86 °F), instead of 31/32 °C (88/90 °F) that are recorded in the rest of the year.
Average temperatures - Port Moresby

Port Moresby	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Port Moresby	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	23	22	22	22	22	22	21	21	22	22	22	23
Max (°C)	31	31	31	31	30	30	29	30	30	31	32	32
Min (°F)	73	72	72	72	72	72	70	70	72	72	72	73
Max (°F)	88	88	88	88	86	86	84	86	86	88	90	90

Here the amount of sunshine is also higher than in other areas of the country.
Sunshine - Port Moresby

Port Moresby	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Port Moresby	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	7	7	8	8	8	9	10	10	10	9	9	8

The sea is always warm enough for swimming throughout the country, although in the southernmost part, where lies the capital, it becomes a bit less warm from July to October, as we can see in the following table.
Sea temperature - Port Moresby

Port Moresby	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Port Moresby	J	F	M	A	M	J	J	A	S	O	N	D
Sea (°C)	29	29	29	29	28	27	26	25	26	26	28	29
Sea (°F)	84	84	84	84	82	81	79	77	79	79	82	84

The interior of the mainland (eastern New Guinea) is crossed by mountains: in the north the Victor Emanuel Range and the Bismarck Mountains, the latter culminating in the 4,509 metres (14,793 feet) high Mount Wilhelm, while in the south we find the Owen Stanley Mountains, whose highest peak is Mount Victoria, 4,038 metres (13,248 feet) high.
At 1,500 metres (5,000 feet) the temperature is pleasant: cool at night, and warm during the day.
Here are the average temperatures of Goroka, located at 1,600 meters above sea level, in the Eastern Highlands province.
Average temperatures - Goroka

Goroka	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Goroka	J	F	M	A	M	J	J	A	S	O	N	D
Min (°C)	16	16	16	16	15	15	15	15	16	15	16	16
Max (°C)	27	26	26	27	26	26	26	26	26	27	27	28
Min (°F)	61	61	61	61	59	59	59	59	61	59	61	61
Max (°F)	81	79	79	81	79	79	79	79	79	81	81	82

In Goroka 1,700 mm (68 in) of rain per year fall; there is a relatively dry season from June to August, in which however some showers are possible.
Average precipitation - Goroka

Goroka	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Year
Goroka	J	F	M	A	M	J	J	A	S	O	N	D	Y
Prec. (mm)	155	214	270	175	150	45	70	50	150	130	145	165	1720
Prec.(in)	6.1	8.4	10.6	6.9	5.9	1.8	2.8	2	5.9	5.1	5.7	6.5	67.7
Days	13	13	12	12	12	12	12	12	12	13	13	13	150

The sun in the mountainous areas shines less often than on the coasts, and the sky is often cloudy.
Sunshine - Goroka

Goroka	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Goroka	J	F	M	A	M	J	J	A	S	O	N	D
Sun (hours)	5	5	4	5	4	5	4	5	5	5	5	5

Above 3,500 metres (11,500 ft), the forest leaves room for a sparse mountain vegetation: here the cold is constant and sometimes it may even snow.
From the mountains, several rivers flow, such as Sepik and Fly, which in lowland areas, often at great distance from the mouth, give rise to marshes and swamps, rich in mangroves and gallery forests.

Papua New Guinea can be affected by tropical cyclones, which in the South Pacific occur from November to mid-May, although they are more likely from November to March. The part of the country that is directly affected is the centre-south. The map below is an indication of the areas that have been affected in the past. The northern areas, however, may be partly affected by an increase in wind, clouds and waves.



The climate of Papua New Guinea is influenced by the so-called ENSO cycle: in the years of El Niño, the rainy season is warmer and drier than normal, and often the monsoon arrives late, while the dry season is cooler than normal in the south; in the years of La Niña, the rainy season from December to April is rainier than normal and can lead to flooding, while the dry season is warmer than normal in the south. During neutral phases (neither El Niño nor La Niña), however, it's more likely for cyclones to form.


The best time to visit Papua New Guinea, at least in the southern coast which includes Port Moresby and is the only one which experiences a real dry season, runs from June to August or September, because it is also the coolest. The months of May, October and November along this coast have little rain as well, but they are a bit hotter.
On the contrary, as we have seen the other parts of the country do not experience a real dry season, in fact they are rainy all year round, and some areas, such as the coast where Lae is located, receive the greatest amount of rainfall even in this period. However, the best period to visit the country as a whole is still from June to August, recalling that in many areas there can be showers and thunderstorms, more or less intense.


All year round, tropics-friendly, loose fitting clothing, sun hat, a scarf for the breeze, a light sweatshirt for the evening, light raincoat or umbrella. For the reef, equipment for snorkeling, water shoes or rubber soled shoes.
In inland areas, around 2,000 metres (6,500 feet), spring/autumn clothes, sweater and jacket for the evening, umbrella. For the highest peaks, warm clothes, down jacket, gloves, hat, hiking boots.