Climate and average weather in Chelmsford
In Chelmsford, the summers are mild, showery, and partly cloudy and the winters are cold, snowy, and mostly cloudy.
Over the course of the year, the temperature in Chelmsford typically varies from 3°C to 21°C, and is rarely below -2°C or above 26°C. July is the hottest month of the year, while January is the coldest.
Based on the travel score, the best time of year to visit Chelmsford for warm-weather activities is from late May to late September.
- Hottest
- Jul
- 21°
- Coldest
- Jan
- 3°
- Wettest
- Aug
- 59 mm
- Driest
- Mar
- 39 mm
- Rain / yr
- 600 mm
- 121 wet days
- Daylight
- 7.6–16.4 h
- shortest–longest
- Elevation
- 33 m
- 51.7°N
- Clearest
- Jul
- 66% cloud
Chelmsford is city in Essex, United Kingdom.
- Density
- 4,339/km²
- people per km²
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
Chelmsford 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 late May to late September.
Temperature through the year
Daily average highs and lows in Chelmsford, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 3.3 months, from June 10 to September 16, with daily high temperatures above 18°C. The hottest month of the year in Chelmsford is July, with an average high of 21°C and low of 14°C.
The cool season lasts 3.9 months, from November 17 to March 14, with daily high temperatures below 10°C. The coldest month of the year in Chelmsford is January, with an average low of 3°C and high of 7°C.
Days typically run about 6°C warmer than nights, with the widest day–night swing (around 8°C) in July.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 7 | 8 | 10 | 13 | 16 | 19 | 21 | 21 | 18 | 15 | 10 | 8 |
| Avg low (°C) | 3 | 3 | 4 | 6 | 9 | 12 | 14 | 14 | 11 | 9 | 5 | 3 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| Jan | 7 | 3 |
| Feb | 8 | 3 |
| Mar | 10 | 4 |
| Apr | 13 | 6 |
| May | 16 | 9 |
| Jun | 19 | 12 |
| Jul | 21 | 14 |
| Aug | 21 | 14 |
| Sep | 18 | 11 |
| Oct | 15 | 9 |
| Nov | 10 | 5 |
| Dec | 8 | 3 |
How hot and cold Chelmsford 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 coldest nights, wind chill pulls the feels-like down to about -2°C (around January 30), with roughly 95 freezing days a year (feels-like at or below 0°C), worst in January.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels-like high (°C) | 7 | 8 | 10 | 13 | 16 | 19 | 21 | 21 | 18 | 14 | 10 | 8 |
| Air high (°C) | 7 | 8 | 10 | 13 | 16 | 19 | 21 | 21 | 18 | 15 | 10 | 8 |
| Feels-like low (°C) | -2 | -2 | 0 | 3 | 7 | 12 | 14 | 14 | 11 | 6 | 2 | -1 |
| Air low (°C) | 3 | 3 | 4 | 6 | 9 | 12 | 14 | 14 | 11 | 9 | 5 | 3 |
| Feels-like high (°C) | Air high (°C) | Feels-like low (°C) | Air low (°C) | |
|---|---|---|---|---|
| Jan | 7 | 7 | -2 | 3 |
| Feb | 8 | 8 | -2 | 3 |
| Mar | 10 | 10 | 0 | 4 |
| Apr | 13 | 13 | 3 | 6 |
| May | 16 | 16 | 7 | 9 |
| Jun | 19 | 19 | 12 | 12 |
| Jul | 21 | 21 | 14 | 14 |
| Aug | 21 | 21 | 14 | 14 |
| Sep | 18 | 18 | 11 | 11 |
| Oct | 14 | 15 | 6 | 9 |
| Nov | 10 | 10 | 2 | 5 |
| Dec | 8 | 8 | -1 | 3 |
Average hourly temperature in Chelmsford
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 July afternoons, near 21°C, and coldest before dawn in January, near 3°C.
Chelmsford weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 7° / 3° | 50 | 10.7 | 0.8 | 8.1 | 0.9 |
| Feb | 8° / 3° | 41 | 9 | 1 | 9.6 | 1.1 |
| Mar | 10° / 4° | 39 | 10 | 0.7 | 11.5 | 2.2 |
| Apr | 13° / 6° | 46 | 10.8 | 0.1 | 13.6 | 3.5 |
| May | 16° / 9° | 51 | 9.8 | 0 | 15.4 | 4.9 |
| Jun | 19° / 12° | 53 | 9.9 | 0 | 16.3 | 5.9 |
| Jul | 21° / 14° | 53 | 10.9 | 0 | 16 | 6.3 |
| Aug | 21° / 14° | 59 | 9.9 | 0 | 14.4 | 6.4 |
| Sep | 18° / 11° | 46 | 8.9 | 0 | 12.4 | 5.9 |
| Oct | 15° / 9° | 55 | 10.5 | 0 | 10.4 | 4.2 |
| Nov | 10° / 5° | 56 | 10.4 | 0.1 | 8.6 | 2.3 |
| Dec | 8° / 3° | 54 | 10.5 | 0.8 | 7.6 | 1.2 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
Chelmsford gets about 600 mm of precipitation a year. On a typical day the chance of rain is often wet, and that barely changes with the seasons — rain is spread fairly evenly through the year.
August is the wettest month by volume, with 59 mm over about 10 wet days; March is the driest, with 39 mm. Some of the cold-season precipitation falls as snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 34 | 32 | 32 | 35 | 33 | 33 | 34 | 32 | 30 | 34 | 34 | 34 |
| Rain days | 11 | 9 | 10 | 11 | 10 | 10 | 11 | 10 | 9 | 11 | 10 | 11 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 34 | 11 |
| Feb | 32 | 9 |
| Mar | 32 | 10 |
| Apr | 35 | 11 |
| May | 33 | 10 |
| Jun | 33 | 10 |
| Jul | 34 | 11 |
| Aug | 32 | 10 |
| Sep | 30 | 9 |
| Oct | 34 | 11 |
| Nov | 34 | 10 |
| Dec | 34 | 11 |
Monthly rainfall
Over a full year, Chelmsford collects about 600 mm of rain across 121 wet days — roughly 50 mm in an average month.
It doesn’t fall evenly. August is the wettest month with 59 mm, while March is the driest at just 39 mm. The three wettest months alone bring about 28% of the year’s total, and some of the cold-season precipitation falls as snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (mm) | 50 | 41 | 39 | 46 | 51 | 53 | 53 | 59 | 46 | 55 | 56 | 54 |
| Rain days | 11 | 9 | 10 | 11 | 10 | 10 | 11 | 10 | 9 | 11 | 10 | 11 |
| Snow days | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Rainfall (mm) | Rain days | Snow days | |
|---|---|---|---|
| Jan | 50 | 11 | 1 |
| Feb | 41 | 9 | 1 |
| Mar | 39 | 10 | 1 |
| Apr | 46 | 11 | 0 |
| May | 51 | 10 | 0 |
| Jun | 53 | 10 | 0 |
| Jul | 53 | 11 | 0 |
| Aug | 59 | 10 | 0 |
| Sep | 46 | 9 | 0 |
| Oct | 55 | 11 | 0 |
| Nov | 56 | 10 | 0 |
| Dec | 54 | 11 | 1 |
Snow in Chelmsford
Average snowy days through the year, the snow-season span, and estimated snowfall — for ski trips and the perennial 'will there be snow at Christmas?' question.
Chelmsford averages about 4 snowy days a year. Snow season runs roughly Nov 27 to Mar 26 — about 3.9 months.
February is snowiest, with roughly 1.1 day of snow and an estimated 4 cm of snowfall. Over the year that adds up to an estimated 11 cm of snow.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Snow days | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
| Snowfall (cm) | 3 | 4 | 2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 2 |
| Snow days | Snowfall (cm) | |
|---|---|---|
| Jan | 1 | 3 |
| Feb | 1 | 4 |
| Mar | 1 | 2 |
| Apr | 0 | 0 |
| May | 0 | 0 |
| Jun | 0 | 0 |
| Jul | 0 | 0 |
| Aug | 0 | 0 |
| Sep | 0 | 0 |
| Oct | 0 | 0 |
| Nov | 0 | 1 |
| Dec | 1 | 2 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In Chelmsford, the average share of the sky covered by clouds shows mild seasonal variation over the course of the year.
The clearer part of the year begins around June 26 and lasts for 2.8 months, ending around September 18. The clearest month is July, when the sky is clear, mostly clear, or partly cloudy 36% of the time on average.
The cloudier part of the year begins around December 14 and lasts for 3.5 months, ending around March 29. The cloudiest month is March, when it is overcast or mostly cloudy 71% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 29 | 29 | 29 | 32 | 33 | 30 | 36 | 35 | 33 | 32 | 31 | 31 |
| Cloudier (%) | 71 | 71 | 71 | 68 | 67 | 70 | 64 | 65 | 67 | 68 | 69 | 69 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 29 | 71 |
| Feb | 29 | 71 |
| Mar | 29 | 71 |
| Apr | 32 | 68 |
| May | 33 | 67 |
| Jun | 30 | 70 |
| Jul | 36 | 64 |
| Aug | 35 | 65 |
| Sep | 33 | 67 |
| Oct | 32 | 68 |
| Nov | 31 | 69 |
| Dec | 31 | 69 |
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 12, brings about 16 h 24 min of light; the shortest, around January 1, only 7 h 36 min — a swing of roughly 8 h 48 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 8.1 | 9.6 | 11.5 | 13.6 | 15.4 | 16.3 | 16.0 | 14.4 | 12.4 | 10.4 | 8.6 | 7.6 |
| Sunrise (AM) | 8:06 | 7:25 | 6:23 | 5:10 | 4:13 | 3:46 | 4:04 | 4:49 | 5:41 | 6:32 | 7:27 | 8:07 |
| Sunset (PM) | 4:09 | 5:01 | 5:53 | 6:46 | 7:36 | 8:11 | 8:04 | 7:15 | 6:04 | 4:54 | 3:59 | 3:42 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 8.1 | 8:06 | 4:09 |
| Feb | 9.6 | 7:25 | 5:01 |
| Mar | 11.5 | 6:23 | 5:53 |
| Apr | 13.6 | 5:10 | 6:46 |
| May | 15.4 | 4:13 | 7:36 |
| Jun | 16.3 | 3:46 | 8:11 |
| Jul | 16.0 | 4:04 | 8:04 |
| Aug | 14.4 | 4:49 | 7:15 |
| Sep | 12.4 | 5:41 | 6:04 |
| Oct | 10.4 | 6:32 | 4:54 |
| Nov | 8.6 | 7:27 | 3:59 |
| Dec | 7.6 | 8:07 | 3:42 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
Chelmsford gets about 5 sunny days a month — gloomy — and it barely shifts through the year, holding between 4 and 5 days every month. Clear skies here are a flat line, not a season.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 5 | 4 | 4 | 5 | 5 | 5 | 5 | 5 | 4 | 5 | 5 | 5 |
| Sky | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy | Gloomy |
| Sunny days | Sky | |
|---|---|---|
| Jan | 5 | Gloomy |
| Feb | 4 | Gloomy |
| Mar | 4 | Gloomy |
| Apr | 5 | Gloomy |
| May | 5 | Gloomy |
| Jun | 5 | Gloomy |
| Jul | 5 | Gloomy |
| Aug | 5 | Gloomy |
| Sep | 4 | Gloomy |
| Oct | 5 | Gloomy |
| Nov | 5 | Gloomy |
| Dec | 5 | Gloomy |
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 Chelmsford, the air stays dry or comfortable essentially all year. Even in August, the muggiest month, it feels humid or worse only about 13% of the time — humidity is not something you need to plan around here.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 100 | 100 | 100 | 100 | 95 | 76 | 51 | 50 | 72 | 89 | 99 | 100 |
| Comfortable (%) | 0 | 0 | 0 | 0 | 5 | 20 | 39 | 37 | 24 | 11 | 1 | 0 |
| Humid (%) | 0 | 0 | 0 | 0 | 0 | 4 | 10 | 13 | 4 | 0 | 0 | 0 |
| Muggy (%) | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 |
| Dry (%) | Comfortable (%) | Humid (%) | Muggy (%) | |
|---|---|---|---|---|
| Jan | 100 | 0 | 0 | 0 |
| Feb | 100 | 0 | 0 | 0 |
| Mar | 100 | 0 | 0 | 0 |
| Apr | 100 | 0 | 0 | 0 |
| May | 95 | 5 | 0 | 0 |
| Jun | 76 | 20 | 4 | 0 |
| Jul | 51 | 39 | 10 | 0 |
| Aug | 50 | 37 | 13 | 1 |
| Sep | 72 | 24 | 4 | 0 |
| Oct | 89 | 11 | 0 | 0 |
| Nov | 99 | 1 | 0 | 0 |
| Dec | 100 | 0 | 0 | 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 Chelmsford is typically light breeze, near 16 km/h, and varies little with the seasons.
The windier part of the year lasts 5.6 months, from around Oct 11 to Mar 30. The windiest month is January, averaging about 18 km/h (light breeze).
The calmer part of the year runs from around Mar 31 to Oct 10, with July the calmest month at about 14 km/h.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 18 | 18 | 17 | 15 | 15 | 14 | 14 | 14 | 15 | 16 | 17 | 18 |
| 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 (km/h) | Feels | |
|---|---|---|
| Jan | 18 | light breeze |
| Feb | 18 | light breeze |
| Mar | 17 | light breeze |
| Apr | 15 | light breeze |
| May | 15 | light breeze |
| Jun | 14 | light breeze |
| Jul | 14 | light breeze |
| Aug | 14 | light breeze |
| Sep | 15 | light breeze |
| Oct | 16 | light breeze |
| Nov | 17 | light breeze |
| Dec | 18 | light breeze |
Best time to visit Chelmsford
To characterize how pleasant the weather is in Chelmsford throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around late September, Chelmsford 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 18°C and 28°C. Based on this score, the best time of year to visit Chelmsford for general outdoor tourist activities is from late May to late September, with a peak score in the last week of July.
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) | 1.0 | 1.2 | 2.2 | 3.5 | 4.9 | 5.9 | 6.3 | 6.4 | 5.9 | 4.2 | 2.3 | 1.2 |
| Rating | poor | poor | poor | poor | fair | good | good | good | good | fair | poor | poor |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 1.0 | poor |
| Feb | 1.2 | poor |
| Mar | 2.2 | poor |
| Apr | 3.5 | poor |
| May | 4.9 | fair |
| Jun | 5.9 | good |
| Jul | 6.3 | good |
| Aug | 6.4 | good |
| Sep | 5.9 | good |
| Oct | 4.2 | fair |
| Nov | 2.3 | poor |
| Dec | 1.2 | poor |
The beach/pool score favors clear, rainless days with daytime highs between 24°C and 34°C. Based on this score, the best time of year to visit Chelmsford for hot-weather activities is from early July to late August, with a peak score in the last week of July.
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 Chelmsford, 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 July (highs near 21°C), the essentials are rain gear and sun protection. In the cold season around January (highs near 7°C), pack a warm layer, a heavy coat and rain gear.
In July, Chelmsford sees daytime highs around 21°C and nights near 14°C. Worth packing: rain gear and sun protection. About 11 days see rain.
Sea temperature near Chelmsford
Average ocean temperature at the nearest coast, month by month, banded into swim-comfort zones — the other half of the beach question.
The sea at the nearest coast (about 47 km away) is warmest in August at about 18°C and coldest in February near 6°C.
The water stays below 20°C all year — cool enough that most swimmers want a wetsuit.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 7 | 6 | 7 | 9 | 12 | 15 | 17 | 18 | 17 | 15 | 12 | 9 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Bracing | Cool | Cool | Cool | Bracing | Bracing | Bracing |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 7 | Bracing |
| Feb | 6 | Bracing |
| Mar | 7 | Bracing |
| Apr | 9 | Bracing |
| May | 12 | Bracing |
| Jun | 15 | Bracing |
| Jul | 17 | Cool |
| Aug | 18 | Cool |
| Sep | 17 | Cool |
| Oct | 15 | Bracing |
| Nov | 12 | Bracing |
| Dec | 9 | Bracing |
UV index (midday) in Chelmsford 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 Chelmsford peaks around August 10 at about 6 (high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near January 1 at about 1 (low).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 6 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 1 | 1 | 3 | 3 | 6 | 6 | 6 | 6 | 4 | 2 | 1 | 1 |
| Level | Low | Low | Moderate | Moderate | High | High | High | High | Moderate | Moderate | Low | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 1 | Low |
| Feb | 1 | Low |
| Mar | 3 | Moderate |
| Apr | 3 | Moderate |
| May | 6 | High |
| Jun | 6 | High |
| Jul | 6 | High |
| Aug | 6 | High |
| Sep | 4 | Moderate |
| Oct | 2 | Moderate |
| Nov | 1 | Low |
| Dec | 1 | Low |
Average hourly UV index in Chelmsford
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 August the burn window is concentrated in the middle of the day: about 7 hours a day reach index 3 (protection recommended), and 1.5 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) | 0 | 0 | 0 | 2.5 | 6.5 | 7.5 | 7.5 | 7 | 4 | 0 | 0 | 0 |
| UV ≥ 6 (h/day) | 0 | 0 | 0 | 0 | 0 | 1 | 1.5 | 1.5 | 0 | 0 | 0 | 0 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 0 | 0 |
| Feb | 0 | 0 |
| Mar | 0 | 0 |
| Apr | 2.5 | 0 |
| May | 6.5 | 0 |
| Jun | 7.5 | 1 |
| Jul | 7.5 | 1.5 |
| Aug | 7 | 1.5 |
| Sep | 4 | 0 |
| Oct | 0 | 0 |
| Nov | 0 | 0 |
| Dec | 0 | 0 |
Growing season
Chelmsford is mild enough that a frost-free day stays more likely than not even in midwinter. Nights are reliably above freezing from about March 9 to November 27 (264 days); outside that window a hard frost is an occasional risk.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 80 | 80 | 92 | 98 | 100 | 100 | 100 | 100 | 100 | 99 | 94 | 83 |
| Frost nights | 31 | 28 | 8 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 9 | 31 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 80 | 31 |
| Feb | 80 | 28 |
| Mar | 92 | 8 |
| Apr | 98 | 0 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 99 | 0 |
| Nov | 94 | 9 |
| Dec | 83 | 31 |
Growing degree days
Growing degree days tally heat above 10°C: each day adds however many degrees its average temperature runs over that threshold, and cold days add nothing. Chelmsford banks about 898 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around July.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°C·days) | 0 | 0 | 0 | 3 | 73 | 158 | 235 | 234 | 147 | 49 | 0 | 0 |
| Growing degree days (°C·days) | |
|---|---|
| Jan | 0 |
| Feb | 0 |
| Mar | 0 |
| Apr | 3 |
| May | 73 |
| Jun | 158 |
| Jul | 235 |
| Aug | 234 |
| Sep | 147 |
| Oct | 49 |
| Nov | 0 |
| Dec | 0 |
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.
Chelmsford receives about 3.1 kWh/m² a day of solar energy on average — moderate — with a clear seasonal swing between 0.6 and 5.5 kWh/m².
The brighter stretch of the year lasts 5.9 months, from around Mar 22 to Sep 17. The brightest month is June, averaging about 5.5 kWh/m² (bright).
The dimmest month is December, down near 0.7 kWh/m² — roughly 88% less than the June peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 0.8 | 1.5 | 2.8 | 4.3 | 5.2 | 5.5 | 5.3 | 4.4 | 3.2 | 1.9 | 1.0 | 0.7 |
| Level | Dim | Dim | Moderate | Bright | Bright | Bright | Bright | Bright | Moderate | Dim | Dim | Dim |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 0.8 | Dim |
| Feb | 1.5 | Dim |
| Mar | 2.8 | Moderate |
| Apr | 4.3 | Bright |
| May | 5.2 | Bright |
| Jun | 5.5 | Bright |
| Jul | 5.3 | Bright |
| Aug | 4.4 | Bright |
| Sep | 3.2 | Moderate |
| Oct | 1.9 | Dim |
| Nov | 1.0 | Dim |
| Dec | 0.7 | Dim |
Where is Chelmsford?
Chelmsford sits at 51.7°N, 0.5°E, 33 m above sea level, in United Kingdom. The nearest listed city is Billericay, 12 km away.
Topography around Chelmsford
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Chelmsford.
Within 3 km, the terrain around Chelmsford has only modest variations in elevation — a maximum elevation change of 53 m around an average of 38 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 117 m; within 80 km, significant variations in elevation — a maximum elevation change of 290 m.
The land around Chelmsford is covered by artificial surfaces (39%), trees (28%) and grassland (21%) within 3 km, cropland (50%), grassland (22%) and trees (20%) within 16 km, and cropland (36%) and grassland (21%) within 80 km.
United Kingdom travel facts
- Travel advisory
- Level 2
- Exercise Increased Caution
- Power plugs
- Type D / G / M
- 230 V · 50 Hz
- Prices
- ≈ 89% of US
- price level, 2025
- GDP per capita
- $57,602
- 2025
- Happiness
- 6.7 / 10
- World Happiness, 2025
- Safe drinking water
- 100%
- of population, 2024
- Homicide rate
- 1.1
- per 100k, 2021
- Road deaths
- 3.2
- 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 Chelmsford (51.7358°, 0.4696°, elevation 33 m), 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. Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).