Climate and average weather in San Juan
In San Juan, the summers are muggy, sweltering, fairly dry, and mostly clear and the winters are warm and partly cloudy.
Over the course of the year, the temperature in San Juan typically varies from 52°F to 98°F, and is rarely below 40°F or above 103°F. August is the hottest month of the year, while January is the coldest.
Based on the travel score, the best times of year to visit San Juan for warm-weather activities are from early January to late March and late October to late December.
- Hottest
- Aug
- 98°
- Coldest
- Jan
- 52°
- Wettest
- Sep
- 3.5 in
- Driest
- Feb
- 0.9 in
- Rain / yr
- 21.4 in
- 74 wet days
- Daylight
- 10.4–13.6 h
- shortest–longest
- Elevation
- 108 ft
- 26.2°N
- Clearest
- Oct
- 41% cloud
San Juan is city in Hidalgo County, Texas, United States.
- Density
- 1,233/km²
- people per km²
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
San Juan weather by month, at a glance
The whole year in one picture — sky, rain, humidity, temperature and travel score. Click any band to jump to its full chart.
Each stripe is one measure across the whole year, stacked so a single day reads top to bottom. The sky band runs overcast grey on top down to clear blue at the base — more blue means sunnier — followed by the rainfall curve, the humidity band, a temperature strip that tints each stretch of the year by how warm its average high is, and the travel-score line at the foot. Scan straight down any date to read that day across every measure at once; the score climbs highest around early January to late March.
Temperature through the year
Daily average highs and lows in San Juan, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 4.2 months, from May 14 to September 18, with daily high temperatures above 92°F. The hottest month of the year in San Juan is August, with an average high of 98°F and low of 78°F.
The cool season lasts 2.6 months, from November 29 to February 14, with daily high temperatures below 76°F. The coldest month of the year in San Juan is January, with an average low of 52°F and high of 72°F.
Days typically run about 19°F warmer than nights year-round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°F) | 72 | 76 | 82 | 88 | 92 | 96 | 98 | 98 | 93 | 87 | 79 | 73 |
| Avg low (°F) | 52 | 56 | 62 | 68 | 73 | 77 | 78 | 78 | 75 | 68 | 60 | 54 |
| Avg high (°F) | Avg low (°F) | |
|---|---|---|
| Jan | 72 | 52 |
| Feb | 76 | 56 |
| Mar | 82 | 62 |
| Apr | 88 | 68 |
| May | 92 | 73 |
| Jun | 96 | 77 |
| Jul | 98 | 78 |
| Aug | 98 | 78 |
| Sep | 93 | 75 |
| Oct | 87 | 68 |
| Nov | 79 | 60 |
| Dec | 73 | 54 |
How hot and cold San Juan really feels
The felt-temperature range through the year — heat index on the day's high (summer humidity), wind chill on the night's low (winter wind). The dashed lines are the plain thermometer; the gap is how much hotter or colder it really feels.
On the hottest afternoons, once humidity is folded in, San Juan feels like about 110°F (around August 6). About 180 days a year carry some heat stress, and 106 of them tip into dangerous heat (feels-like above 102°F), peaking in August.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels-like high (°F) | 72 | 76 | 82 | 89 | 98 | 106 | 108 | 108 | 100 | 89 | 79 | 73 |
| Air high (°F) | 72 | 76 | 82 | 88 | 92 | 96 | 98 | 98 | 93 | 87 | 79 | 73 |
| Feels-like low (°F) | 52 | 56 | 62 | 68 | 73 | 77 | 78 | 78 | 75 | 68 | 60 | 54 |
| Air low (°F) | 52 | 56 | 62 | 68 | 73 | 77 | 78 | 78 | 75 | 68 | 60 | 54 |
| Feels-like high (°F) | Air high (°F) | Feels-like low (°F) | Air low (°F) | |
|---|---|---|---|---|
| Jan | 72 | 72 | 52 | 52 |
| Feb | 76 | 76 | 56 | 56 |
| Mar | 82 | 82 | 62 | 62 |
| Apr | 89 | 88 | 68 | 68 |
| May | 98 | 92 | 73 | 73 |
| Jun | 106 | 96 | 77 | 77 |
| Jul | 108 | 98 | 78 | 78 |
| Aug | 108 | 98 | 78 | 78 |
| Sep | 100 | 93 | 75 | 75 |
| Oct | 89 | 87 | 68 | 68 |
| Nov | 79 | 79 | 60 | 60 |
| Dec | 73 | 73 | 54 | 54 |
Average hourly temperature in San Juan
A compact picture of the whole year, hour by hour: each column is a day, each row an hour, and the color is the modeled average temperature. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
Read left to right for the day of the year and top to bottom for the hour of the day; the color is the modeled temperature, cool blues through to hot reds on the same scale as the other charts. A vertical slice is a single day's swing — coolest just before dawn, warmest in the mid-afternoon — while a horizontal slice follows one hour across the seasons. The darker overlay marks night and the lighter one the twilight around sunrise and sunset. Colors run warmest on August afternoons, near 98°F, and coldest before dawn in January, near 52°F.
San Juan weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 72° / 52° | 1.0 | 4.4 | 10.5 | 7.5 |
| Feb | 76° / 56° | 0.9 | 4.4 | 11.1 | 7.7 |
| Mar | 82° / 62° | 1.4 | 5.2 | 11.8 | 6.8 |
| Apr | 88° / 68° | 1.7 | 5.3 | 12.6 | 5.0 |
| May | 92° / 73° | 2.2 | 6.6 | 13.3 | 3.5 |
| Jun | 96° / 77° | 2.0 | 7.1 | 13.6 | 2.4 |
| Jul | 98° / 78° | 2.1 | 5.8 | 13.5 | 2.0 |
| Aug | 98° / 78° | 1.6 | 6.8 | 12.9 | 1.8 |
| Sep | 93° / 75° | 3.5 | 11.8 | 12.2 | 3.1 |
| Oct | 87° / 68° | 2.3 | 6.7 | 11.4 | 5.2 |
| Nov | 79° / 60° | 1.4 | 5.3 | 10.7 | 7.5 |
| Dec | 73° / 54° | 1.2 | 5.1 | 10.4 | 7.6 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
San Juan gets about 21.4 in of precipitation a year. On a typical day the chance of rain is some rain, but that rises and falls sharply with the seasons.
The wetter season lasts 2.1 months, from around Aug 16 to Oct 18, peaking in September at about 44% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Nov 30.
September is the wettest month by volume, with 3.5 in over about 12 wet days; February is the driest, with 0.9 in.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 15 | 15 | 17 | 17 | 21 | 24 | 19 | 23 | 38 | 22 | 18 | 16 |
| Rain days | 4 | 4 | 5 | 5 | 7 | 7 | 6 | 7 | 12 | 7 | 5 | 5 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 15 | 4 |
| Feb | 15 | 4 |
| Mar | 17 | 5 |
| Apr | 17 | 5 |
| May | 21 | 7 |
| Jun | 24 | 7 |
| Jul | 19 | 6 |
| Aug | 23 | 7 |
| Sep | 38 | 12 |
| Oct | 22 | 7 |
| Nov | 18 | 5 |
| Dec | 16 | 5 |
Monthly rainfall
Over a full year, San Juan collects about 21.4 in of rain across 74 wet days — roughly 1.8 in in an average month.
It doesn’t fall evenly. September is the wettest month with 3.5 in, while February is the driest at just 0.9 in. The three wettest months alone bring about 37% of the year’s total.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (in) | 1.0 | 0.9 | 1.4 | 1.7 | 2.2 | 2.0 | 2.1 | 1.6 | 3.5 | 2.3 | 1.4 | 1.2 |
| Rain days | 4 | 4 | 5 | 5 | 7 | 7 | 6 | 7 | 12 | 7 | 5 | 5 |
| Rainfall (in) | Rain days | |
|---|---|---|
| Jan | 1.0 | 4 |
| Feb | 0.9 | 4 |
| Mar | 1.4 | 5 |
| Apr | 1.7 | 5 |
| May | 2.2 | 7 |
| Jun | 2.0 | 7 |
| Jul | 2.1 | 6 |
| Aug | 1.6 | 7 |
| Sep | 3.5 | 12 |
| Oct | 2.3 | 7 |
| Nov | 1.4 | 5 |
| Dec | 1.2 | 5 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In San Juan, the average share of the sky covered by clouds shows significant seasonal variation over the course of the year.
The clearer part of the year begins around May 11 and lasts for 3.6 months, ending around August 28. The clearest month is June, when the sky is clear, mostly clear, or partly cloudy 75% of the time on average.
The cloudier part of the year begins around November 6 and lasts for 6.1 months, ending around May 10. The cloudiest month is January, when it is overcast or mostly cloudy 52% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 48 | 52 | 53 | 55 | 65 | 75 | 69 | 67 | 61 | 70 | 59 | 52 |
| Cloudier (%) | 52 | 48 | 47 | 45 | 35 | 25 | 31 | 33 | 39 | 30 | 41 | 48 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 48 | 52 |
| Feb | 52 | 48 |
| Mar | 53 | 47 |
| Apr | 55 | 45 |
| May | 65 | 35 |
| Jun | 75 | 25 |
| Jul | 69 | 31 |
| Aug | 67 | 33 |
| Sep | 61 | 39 |
| Oct | 70 | 30 |
| Nov | 59 | 41 |
| Dec | 52 | 48 |
Daylight, sunrise and sunset
Hours of daylight through the year, with sunrise and sunset times.
The gold band is daylight — sunrise runs along its lower edge, sunset along the upper — so it widens toward summer and pinches toward winter, with night the dark area above and below. The longest day, around June 5, brings about 13 h 36 min of light; the shortest, around January 1, only 10 h 24 min — a swing of roughly 3 h 12 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 10.5 | 11.1 | 11.8 | 12.6 | 13.3 | 13.6 | 13.5 | 12.9 | 12.2 | 11.4 | 10.7 | 10.4 |
| Sunrise (AM) | 7:26 | 7:15 | 6:48 | 6:14 | 5:50 | 5:44 | 5:53 | 6:09 | 6:22 | 6:37 | 6:57 | 7:18 |
| Sunset (PM) | 5:58 | 6:20 | 6:37 | 6:51 | 7:07 | 7:22 | 7:23 | 7:05 | 6:32 | 5:59 | 5:39 | 5:40 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 10.5 | 7:26 | 5:58 |
| Feb | 11.1 | 7:15 | 6:20 |
| Mar | 11.8 | 6:48 | 6:37 |
| Apr | 12.6 | 6:14 | 6:51 |
| May | 13.3 | 5:50 | 7:07 |
| Jun | 13.6 | 5:44 | 7:22 |
| Jul | 13.5 | 5:53 | 7:23 |
| Aug | 12.9 | 6:09 | 7:05 |
| Sep | 12.2 | 6:22 | 6:32 |
| Oct | 11.4 | 6:37 | 5:59 |
| Nov | 10.7 | 6:57 | 5:39 |
| Dec | 10.4 | 7:18 | 5:40 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
San Juan averages about 14 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 11 and 17 days.
The sunnier stretch runs 3.2 months, from around May 21 to Aug 24. The sunniest month is June, with roughly 17 sunny days (bright).
The greyest month is January, down near 12 sunny days — about 29% fewer than the June peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 12 | 11 | 12 | 12 | 14 | 16 | 17 | 15 | 13 | 16 | 13 | 13 |
| Sky | Mixed | Mixed | Mixed | Mixed | Mixed | Bright | Bright | Mixed | Mixed | Bright | Mixed | Mixed |
| Sunny days | Sky | |
|---|---|---|
| Jan | 12 | Mixed |
| Feb | 11 | Mixed |
| Mar | 12 | Mixed |
| Apr | 12 | Mixed |
| May | 14 | Mixed |
| Jun | 16 | Bright |
| Jul | 17 | Bright |
| Aug | 15 | Mixed |
| Sep | 13 | Mixed |
| Oct | 16 | Bright |
| Nov | 13 | Mixed |
| Dec | 13 | Mixed |
Humidity comfort
Share of days at each humidity comfort level, based on the dew point — the measure that tracks how muggy it actually feels.
Humidity comfort is graded by the dew point — the temperature at which the air would be fully saturated — because it tracks how muggy it actually feels far better than relative humidity does. A low dew point feels dry and crisp; a high one feels sticky and oppressive no matter the reading on a humidity gauge.
In San Juan, how humid it feels changes dramatically over the year.
The more humid part of the year lasts 6.5 months, from around April 9 to October 23. The muggiest month is June, when the air feels humid, muggy or worse about 100% of the time.
The most comfortable stretch runs from around October 24 to April 8, and January is the most comfortable month — the air is dry or comfortable 78% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 62 | 50 | 32 | 16 | 3 | 0 | 0 | 0 | 1 | 14 | 34 | 57 |
| Comfortable (%) | 17 | 16 | 15 | 10 | 4 | 0 | 0 | 0 | 3 | 9 | 16 | 13 |
| Humid (%) | 15 | 21 | 20 | 17 | 7 | 1 | 0 | 1 | 7 | 17 | 19 | 16 |
| Muggy (%) | 7 | 14 | 30 | 36 | 25 | 11 | 7 | 6 | 13 | 24 | 24 | 13 |
| Oppressive (%) | 0 | 0 | 3 | 20 | 56 | 75 | 83 | 82 | 59 | 32 | 7 | 1 |
| Miserable (%) | 0 | 0 | 0 | 0 | 4 | 12 | 10 | 11 | 17 | 4 | 0 | 0 |
| Dry (%) | Comfortable (%) | Humid (%) | Muggy (%) | Oppressive (%) | Miserable (%) | |
|---|---|---|---|---|---|---|
| Jan | 62 | 17 | 15 | 7 | 0 | 0 |
| Feb | 50 | 16 | 21 | 14 | 0 | 0 |
| Mar | 32 | 15 | 20 | 30 | 3 | 0 |
| Apr | 16 | 10 | 17 | 36 | 20 | 0 |
| May | 3 | 4 | 7 | 25 | 56 | 4 |
| Jun | 0 | 0 | 1 | 11 | 75 | 12 |
| Jul | 0 | 0 | 0 | 7 | 83 | 10 |
| Aug | 0 | 0 | 1 | 6 | 82 | 11 |
| Sep | 1 | 3 | 7 | 13 | 59 | 17 |
| Oct | 14 | 9 | 17 | 24 | 32 | 4 |
| Nov | 34 | 16 | 19 | 24 | 7 | 0 |
| Dec | 57 | 13 | 16 | 13 | 1 | 0 |
Wind
Average wind speed through the year, banded into plain-language speed zones so a number reads as 'breezy' or 'calm' without knowing the scale.
This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.
Across the year, average wind speed in San Juan is typically light breeze, near 10 mph, and varies moderately with the seasons.
The windier part of the year lasts 6.0 months, from around Feb 16 to Aug 17. The windiest month is May, averaging about 12 mph (light breeze).
The calmer part of the year runs from around Aug 18 to Feb 15, with September the calmest month at about 8 mph.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (mph) | 10 | 10 | 11 | 12 | 12 | 12 | 12 | 10 | 8 | 9 | 9 | 9 |
| Feels | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze |
| Wind speed (mph) | Feels | |
|---|---|---|
| Jan | 10 | light breeze |
| Feb | 10 | light breeze |
| Mar | 11 | light breeze |
| Apr | 12 | light breeze |
| May | 12 | light breeze |
| Jun | 12 | light breeze |
| Jul | 12 | light breeze |
| Aug | 10 | light breeze |
| Sep | 8 | light breeze |
| Oct | 9 | light breeze |
| Nov | 9 | light breeze |
| Dec | 9 | light breeze |
Best time to visit San Juan
To characterize how pleasant the weather is in San Juan throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around mid March, San Juan is still near the tail of its best-weather window — great conditions with the peak-season crowds already thinning.
Inferred from the travel-score curve; month-by-month visitor numbers are a planned addition.
The travel score favors clear, rainless days with daytime highs between 64°F and 82°F. Based on this score, the best time of year to visit San Juan for general outdoor tourist activities is from late October to late March, with a peak score in the last week of November.
The travel score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Travel score (0–10) | 7.5 | 7.7 | 6.8 | 5.0 | 3.5 | 2.4 | 2.0 | 1.9 | 3.1 | 5.2 | 7.4 | 7.6 |
| Rating | ideal | ideal | good | fair | fair | poor | poor | poor | poor | fair | good | ideal |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 7.5 | ideal |
| Feb | 7.7 | ideal |
| Mar | 6.8 | good |
| Apr | 5.0 | fair |
| May | 3.5 | fair |
| Jun | 2.4 | poor |
| Jul | 2.0 | poor |
| Aug | 1.9 | poor |
| Sep | 3.1 | poor |
| Oct | 5.2 | fair |
| Nov | 7.4 | good |
| Dec | 7.6 | ideal |
The beach/pool score favors clear, rainless days with daytime highs between 75°F and 93°F. Based on this score, the best times of year to visit San Juan for hot-weather activities run from early February to late May and again from late September to early December, with a peak score in the last week of October.
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
What to pack for San Juan, by month
Month by month, what's worth putting in the bag — from the temperature range, rain chance, sun and wind. Tap a month for a quick packing note.
For a warm-season trip around August (highs near 98°F), the essentials are light clothes and sun protection. In the cold season around January (highs near 72°F), pack light clothes.
In August, San Juan sees daytime highs around 98°F and nights near 78°F. Pack light clothes and sun protection. About 7 days see rain.
UV index (midday) in San Juan by month
Clear-sky midday UV index through the year, shaded by the WHO exposure levels — how much sun protection each month calls for.
Under clear skies, the midday UV index in San Juan peaks around June 21 at about 12 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 at about 5 (moderate).
The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 5 | 7 | 8 | 11 | 9 | 12 | 11 | 11 | 10 | 8 | 6 | 5 |
| Level | Moderate | High | Very high | Extreme | Very high | Extreme | Extreme | Extreme | Very high | Very high | High | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 5 | Moderate |
| Feb | 7 | High |
| Mar | 8 | Very high |
| Apr | 11 | Extreme |
| May | 9 | Very high |
| Jun | 12 | Extreme |
| Jul | 11 | Extreme |
| Aug | 11 | Extreme |
| Sep | 10 | Very high |
| Oct | 8 | Very high |
| Nov | 6 | High |
| Dec | 5 | Moderate |
Average hourly UV index in San Juan
Modeled clear-sky UV for every hour of every day — when in the day sun protection actually matters.
The whole year hour by hour: each column is a day, each row an hour, and the color is the modeled clear-sky UV index — the midday peak scaled down as the sun sits lower in the sky. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
UV falls off far faster than brightness as the sun drops, so even in June the burn window is concentrated in the middle of the day: about 8.5 hours a day reach index 3 (protection recommended), and 6.5 hours reach 6 or more. Mornings and late afternoons stay comparatively gentle year round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV ≥ 3 (h/day) | 4.5 | 6 | 7 | 8 | 8 | 8.5 | 8.5 | 8 | 7.5 | 6.5 | 5.5 | 4.5 |
| UV ≥ 6 (h/day) | 0 | 2.5 | 4 | 6 | 5.5 | 6.5 | 6 | 6 | 5 | 3.5 | 0 | 0 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 4.5 | 0 |
| Feb | 6 | 2.5 |
| Mar | 7 | 4 |
| Apr | 8 | 6 |
| May | 8 | 5.5 |
| Jun | 8.5 | 6.5 |
| Jul | 8.5 | 6 |
| Aug | 8 | 6 |
| Sep | 7.5 | 5 |
| Oct | 6.5 | 3.5 |
| Nov | 5.5 | 0 |
| Dec | 4.5 | 0 |
Air quality in San Juan by month
Average fine-particle pollution (PM2.5) through the year — so you can see which months the air is worst, not just the yearly average.
Air quality in San Juan is worst in July — around 26 µg/m³ PM2.5 (moderate), about 3.5× the cleanest month (November, 7 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 9 | 10 | 11 | 13 | 20 | 21 | 26 | 19 | 12 | 8 | 7 | 9 |
| Level | Good | Good | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 9 | Good |
| Feb | 10 | Good |
| Mar | 11 | Good |
| Apr | 13 | Moderate |
| May | 20 | Moderate |
| Jun | 21 | Moderate |
| Jul | 26 | Moderate |
| Aug | 19 | Moderate |
| Sep | 12 | Moderate |
| Oct | 8 | Good |
| Nov | 7 | Good |
| Dec | 9 | Good |
Growing season
San Juan is frost-free year round — even the coldest nights rarely reach freezing, so there is no start or end to the growing season.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 99 | 99 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 99 |
| Frost nights | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 99 | 0 |
| Feb | 99 | 0 |
| Mar | 100 | 0 |
| Apr | 100 | 0 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 100 | 0 |
| Nov | 100 | 0 |
| Dec | 99 | 0 |
Growing degree days
Growing degree days tally heat above 50°F: each day adds however many degrees its average temperature runs over that threshold, and cold days add nothing. San Juan banks about 9,673 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around August.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°F·days) | 376 | 457 | 680 | 832 | 1,022 | 1,099 | 1,167 | 1,174 | 1,008 | 856 | 588 | 414 |
| Growing degree days (°F·days) | |
|---|---|
| Jan | 376 |
| Feb | 457 |
| Mar | 680 |
| Apr | 832 |
| May | 1,022 |
| Jun | 1,099 |
| Jul | 1,167 |
| Aug | 1,174 |
| Sep | 1,008 |
| Oct | 856 |
| Nov | 588 |
| Dec | 414 |
Solar energy
Average daily shortwave solar energy reaching the ground, banded into brightness zones so the number means something at a glance.
Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.
San Juan receives about 5.1 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 3.1 and 6.8 kWh/m².
The brighter stretch of the year lasts 6.3 months, from around Mar 23 to Sep 30. The brightest month is July, averaging about 6.8 kWh/m² (intense).
The dimmest month is December, down near 3.1 kWh/m² — roughly 54% less than the July peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 3.3 | 4.0 | 4.8 | 5.8 | 6.3 | 6.7 | 6.8 | 6.4 | 5.3 | 4.6 | 3.5 | 3.1 |
| Level | Moderate | Bright | Bright | Bright | Intense | Intense | Intense | Intense | Bright | Bright | Moderate | Moderate |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 3.3 | Moderate |
| Feb | 4.0 | Bright |
| Mar | 4.8 | Bright |
| Apr | 5.8 | Bright |
| May | 6.3 | Intense |
| Jun | 6.7 | Intense |
| Jul | 6.8 | Intense |
| Aug | 6.4 | Intense |
| Sep | 5.3 | Bright |
| Oct | 4.6 | Bright |
| Nov | 3.5 | Moderate |
| Dec | 3.1 | Moderate |
Where is San Juan?
San Juan sits at 26.2°N, 98.2°W, 108 ft above sea level, in United States. The nearest listed city is Pharr, 1.9 mi away.
Topography around San Juan
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of San Juan.
Within 2 miles, the terrain around San Juan has only modest variations in elevation — a maximum elevation change of 52 ft around an average of 108 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 167 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,027 ft.
The land around San Juan is covered by artificial surfaces (49%) and trees (24%) within 2 miles, cropland (31%), artificial surfaces (25%) and trees (22%) within 10 miles, and cropland (38%) and grassland (24%) within 50 miles.
United States travel facts
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 100% of US
- price level, 2025
- GDP per capita
- $90,027
- 2025
- Happiness
- 6.8 / 10
- World Happiness, 2025
- Safe drinking water
- 98%
- of population, 2024
- Homicide rate
- 5.8
- per 100k, 2023
- Road deaths
- 12.7
- per 100k/yr, 2019
- Income group
- High
- World Bank
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for San Juan (26.1892°, -98.1553°, elevation 108 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).