Climate and Average Weather Year Round in Si Ma Cai Vietnam

In Si Ma Cai, the wet season is warm, muggy, and overcast and the dry season is comfortable and mostly clear. Over the course of the year, the temperature typically varies from 44°F to 83°F and is rarely below 36°F or above 89°F.

Based on the tourism score, the best times of year to visit Si Ma Cai for warm-weather activities are from mid March to mid May and from mid September to late October.

The warm season lasts for 5.6 months, from April 4 to September 21, with an average daily high temperature above 79°F. The hottest month of the year in Si Ma Cai is June, with an average high of 83°F and low of 69°F.

The cool season lasts for 2.4 months, from November 29 to February 10, with an average daily high temperature below 66°F. The coldest month of the year in Si Ma Cai is January, with an average low of 44°F and high of 62°F.

In Si Ma Cai, the average percentage of the sky covered by clouds experiences extreme seasonal variation over the course of the year.

The clearer part of the year in Si Ma Cai begins around September 27 and lasts for 7.5 months, ending around May 10.

The clearest month of the year in Si Ma Cai is December, during which on average the sky is clear, mostly clear, or partly cloudy 67% of the time.

The cloudier part of the year begins around May 10 and lasts for 4.6 months, ending around September 27.

The cloudiest month of the year in Si Ma Cai is July, during which on average the sky is overcast or mostly cloudy 88% of the time.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Si Ma Cai varies very significantly throughout the year.

The wetter season lasts 4.9 months, from April 29 to September 24, with a greater than 33% chance of a given day being a wet day. The month with the most wet days in Si Ma Cai is July, with an average of 18.2 days with at least 0.04 inches of precipitation.

The drier season lasts 7.1 months, from September 24 to April 29. The month with the fewest wet days in Si Ma Cai is December, with an average of 1.9 days with at least 0.04 inches of precipitation.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. The month with the most days of rain alone in Si Ma Cai is July, with an average of 18.2 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 61% on August 1.

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Si Ma Cai experiences extreme seasonal variation in monthly rainfall.

Rain falls throughout the year in Si Ma Cai. The month with the most rain in Si Ma Cai is August, with an average rainfall of 8.5 inches.

The month with the least rain in Si Ma Cai is January, with an average rainfall of 0.4 inches.

The length of the day in Si Ma Cai varies over the course of the year. In 2024, the shortest day is December 21, with 10 hours, 45 minutes of daylight; the longest day is June 21, with 13 hours, 32 minutes of daylight.

The earliest sunrise is at 5:17 AM on June 7, and the latest sunrise is 1 hour, 28 minutes later at 6:45 AM on January 15. The earliest sunset is at 5:17 PM on November 27, and the latest sunset is 1 hour, 35 minutes later at 6:51 PM on July 3.

Daylight saving time (DST) is not observed in Si Ma Cai during 2024.

The figure below presents a compact representation of key lunar data for 2024. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases.

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

Si Ma Cai experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 6.0 months, from April 20 to October 19, during which time the comfort level is muggy, oppressive, or miserable at least 25% of the time. The month with the most muggy days in Si Ma Cai is July, with 30.5 days that are muggy or worse.

The month with the fewest muggy days in Si Ma Cai is January, with 0.0 days that are muggy or worse.

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in Si Ma Cai does not vary significantly over the course of the year, remaining within 0.4 miles per hour of 4.2 miles per hour throughout.

The predominant average hourly wind direction in Si Ma Cai varies throughout the year.

The wind is most often from the south for 3.8 months, from April 13 to August 8, with a peak percentage of 55% on July 1. The wind is most often from the east for 8.2 months, from August 8 to April 13, with a peak percentage of 55% on January 1.

To characterize how pleasant the weather is in Si Ma Cai throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best times of year to visit Si Ma Cai for general outdoor tourist activities are from mid March to mid May and from mid September to late October, with a peak score in the third week of April.

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best times of year to visit Si Ma Cai for hot-weather activities are from late April to late July and from early August to mid September, with a peak score in the third week of May.

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

Temperatures in Si Ma Cai are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences some seasonal variation over the course of the year.

The brighter period of the year lasts for 2.0 months, from March 21 to May 23, with an average daily incident shortwave energy per square meter above 5.4 kWh. The brightest month of the year in Si Ma Cai is April, with an average of 5.8 kWh.

The darker period of the year lasts for 2.3 months, from November 22 to February 3, with an average daily incident shortwave energy per square meter below 4.1 kWh. The darkest month of the year in Si Ma Cai is January, with an average of 3.7 kWh.

For the purposes of this report, the geographical coordinates of Si Ma Cai are 22.695 deg latitude, 104.279 deg longitude, and 3,494 ft elevation.

The topography within 2 miles of Si Ma Cai contains large variations in elevation, with a maximum elevation change of 3,186 feet and an average elevation above sea level of 3,641 feet. Within 10 miles contains large variations in elevation (6,243 feet). Within 50 miles also contains extreme variations in elevation (10,062 feet).

The area within 2 miles of Si Ma Cai is covered by cropland (50%) and trees (36%), within 10 miles by cropland (40%) and trees (33%), and within 50 miles by trees (49%) and cropland (23%).