Climate and Average Weather Year Round in Chi’an China

In Chi’an, the summers are hot, oppressive, wet, and mostly cloudy and the winters are very cold and partly cloudy. Over the course of the year, the temperature typically varies from 34°F to 92°F and is rarely below 26°F or above 97°F.

Based on the tourism score, the best time of year to visit Chi’an for warm-weather activities is from mid September to mid October.

The hot season lasts for 3.0 months, from June 10 to September 12, with an average daily high temperature above 83°F. The hottest month of the year in Chi’an is July, with an average high of 91°F and low of 77°F.

The cool season lasts for 3.0 months, from December 3 to March 3, with an average daily high temperature below 57°F. The coldest month of the year in Chi’an is January, with an average low of 34°F and high of 49°F.

In Chi’an, 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 Chi’an begins around September 3 and lasts for 6.4 months, ending around March 14.

The clearest month of the year in Chi’an is October, during which on average the sky is clear, mostly clear, or partly cloudy 71% of the time.

The cloudier part of the year begins around March 14 and lasts for 5.6 months, ending around September 3.

The cloudiest month of the year in Chi’an is July, during which on average the sky is overcast or mostly cloudy 72% 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 Chi’an varies significantly throughout the year.

The wetter season lasts 6.9 months, from February 16 to September 13, with a greater than 32% chance of a given day being a wet day. The month with the most wet days in Chi’an is June, with an average of 14.5 days with at least 0.04 inches of precipitation.

The drier season lasts 5.1 months, from September 13 to February 16. The month with the fewest wet days in Chi’an is December, with an average of 4.7 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 Chi’an is June, with an average of 14.5 days. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 51% on June 22.

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. Chi’an experiences extreme seasonal variation in monthly rainfall.

Rain falls throughout the year in Chi’an. The month with the most rain in Chi’an is June, with an average rainfall of 7.9 inches.

The month with the least rain in Chi’an is December, with an average rainfall of 1.3 inches.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Chi’an experiences some seasonal variation in monthly snowfall.

The snowy period of the year lasts for 1.6 months, from December 25 to February 14, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow in Chi’an is January, with an average snowfall of 1.5 inches.

The snowless period of the year lasts for 10 months, from February 14 to December 25. The least snow falls around July 19, with an average total accumulation of 0.0 inches.

The length of the day in Chi’an varies significantly over the course of the year. In 2024, the shortest day is December 21, with 10 hours, 17 minutes of daylight; the longest day is June 21, with 14 hours, 1 minute of daylight.

The earliest sunrise is at 5:00 AM on June 11, and the latest sunrise is 1 hour, 55 minutes later at 6:55 AM on January 11. The earliest sunset is at 5:01 PM on December 2, and the latest sunset is 2 hours, 2 minutes later at 7:03 PM on July 1.

Daylight saving time (DST) is not observed in Chi’an 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.

Chi’an experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 5.2 months, from May 2 to October 9, 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 Chi’an is July, with 30.8 days that are muggy or worse.

The month with the fewest muggy days in Chi’an 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 Chi’an experiences mild seasonal variation over the course of the year.

The windier part of the year lasts for 3.5 months, from January 27 to May 12, with average wind speeds of more than 6.7 miles per hour. The windiest month of the year in Chi’an is March, with an average hourly wind speed of 7.3 miles per hour.

The calmer time of year lasts for 8.5 months, from May 12 to January 27. The calmest month of the year in Chi’an is June, with an average hourly wind speed of 6.1 miles per hour.

The predominant average hourly wind direction in Chi’an varies throughout the year.

The wind is most often from the south for 4.9 months, from March 20 to August 16, with a peak percentage of 51% on July 13. The wind is most often from the east for 1.1 months, from August 16 to September 18 and for 2.4 weeks, from September 25 to October 12, with a peak percentage of 43% on October 7. The wind is most often from the north for 1.0 weeks, from September 18 to September 25 and for 5.3 months, from October 12 to March 20, with a peak percentage of 41% on September 23.

To characterize how pleasant the weather is in Chi’an 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 time of year to visit Chi’an for general outdoor tourist activities is from mid September to mid October, with a peak score in the last week of September.

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Chi’an for hot-weather activities is from mid July to mid September, with a peak score in the last week of August.

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).

The growing season in Chi’an typically lasts for 9.2 months (279 days), from around February 26 to around December 1, rarely starting before February 3 or after March 20, and rarely ending before November 13 or after December 20.

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.

Based on growing degree days alone, the first spring blooms in Chi’an should appear around February 29, only rarely appearing before February 13 or after March 20.

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 4.9 months, from April 22 to September 18, with an average daily incident shortwave energy per square meter above 5.1 kWh. The brightest month of the year in Chi’an is May, with an average of 5.5 kWh.

The darker period of the year lasts for 2.9 months, from November 11 to February 7, with an average daily incident shortwave energy per square meter below 3.6 kWh. The darkest month of the year in Chi’an is December, with an average of 3.1 kWh.

For the purposes of this report, the geographical coordinates of Chi’an are 29.145 deg latitude, 120.030 deg longitude, and 269 ft elevation.

The topography within 2 miles of Chi’an contains significant variations in elevation, with a maximum elevation change of 715 feet and an average elevation above sea level of 333 feet. Within 10 miles contains significant variations in elevation (2,825 feet). Within 50 miles contains large variations in elevation (5,115 feet).

The area within 2 miles of Chi’an is covered by cropland (49%) and trees (43%), within 10 miles by trees (65%) and cropland (29%), and within 50 miles by trees (72%) and cropland (20%).