Gambridge Go-Karts
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gambridge Go-Karts clear sky chart from 2005-11-06 to 2025-11-03.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	14% 10% 4 9% 5% 5% 4 4 5% 7% 33%	127558
	Night	15% 11% 4 10% 5% 5% 5% 4 5% 6% 30%	122444
Transparency	Day	50% 6% 12% 21% 11% 1	131146
	Night	53% 6% 12% 19% 10% 1	126944
Seeing	Day	19% 11% 28% 26% 13% 4	16015
	Night	20% 9% 30% 28% 11% 1	24953

By Month

Percentage Cloud Cover NE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	12% 14% 6% 14% 6% 6% 5% 4 5% 5% 25%	3597
	11th to 20th	Day	9% 16% 8% 17% 10% 9% 6% 4 4 5% 13%	3778
	21st to end	Day	13% 18% 7% 13% 7% 6% 5% 4 5% 6% 17%	4466
February	1st to 10th	Day	12% 16% 5% 13% 8% 6% 5% 4 5% 5% 22%	1800
	11th to 20th	Day	11% 14% 6% 13% 6% 5% 4 4 5% 7% 25%	1753
	21st to end	Day	15% 15% 5% 10% 7% 6% 4 3 6% 6% 23%	1518
March	1st to 10th	Day	18% 10% 4 10% 7% 4 4 3 5% 5% 30%	4932
	11th to 20th	Day	11% 11% 5% 10% 6% 6% 6% 4 6% 7% 28%	4980
	21st to end	Day	18% 10% 3 9% 5% 4 3 3 4 5% 35%	5465
April	1st to 10th	Day	18% 11% 3 9% 5% 5% 4 3 4 6% 31%	2380
	11th to 20th	Day	19% 10% 3 6% 4 4 4 3 5% 6% 37%	2449
	21st to end	Day	18% 10% 3 8% 5% 4 4 3 4 6% 35%	2600
May	1st to 10th	Day	15% 8% 3 8% 5% 5% 5% 3 6% 7% 34%	5972
	11th to 20th	Day	14% 10% 3 7% 4 5% 4 4 5% 7% 38%	6318
	21st to end	Day	19% 9% 3 7% 4 4 4 3 5% 7% 36%	6949
June	1st to 10th	Day	16% 7% 2 6% 5% 5% 5% 4 6% 8% 37%	2800
	11th to 20th	Day	12% 5% 2 6% 5% 4 5% 5% 7% 9% 40%	2847
	21st to end	Day	15% 6% 2 7% 5% 4 4 4 6% 8% 39%	3000
July	1st to 10th	Day	11% 6% 2 6% 5% 5% 5% 5% 7% 9% 40%	6599
	11th to 20th	Day	9% 5% 2 6% 4 4 4 3 6% 8% 49%	6360
	21st to end	Day	7% 5% 2 5% 4 4 5% 4 6% 9% 48%	6635
August	1st to 10th	Day	13% 8% 3 7% 4 4 4 4 7% 8% 39%	4234
	11th to 20th	Day	12% 7% 2 6% 4 4 5% 4 7% 10% 38%	4174
	21st to end	Day	8% 6% 2 6% 4 4 4 4 7% 9% 45%	4489
September	1st to 10th	Day	13% 6% 2 6% 5% 5% 5% 3 6% 7% 43%	2400
	11th to 20th	Day	11% 6% 2 5% 4 4 4 3 5% 8% 48%	2307
	21st to end	Day	15% 7% 3 7% 5% 5% 5% 4 5% 6% 38%	2145
October	1st to 10th	Day	18% 8% 4 8% 4 4 4 3 5% 6% 36%	2000
	11th to 20th	Day	22% 11% 3 8% 5% 3 4 4 5% 6% 28%	2000
	21st to end	Day	24% 12% 4 9% 5% 5% 4 4 5% 6% 23%	2200
November	1st to 10th	Day	16% 12% 4 8% 5% 5% 5% 3 5% 7% 29%	1665
	11th to 20th	Day	16% 15% 4 9% 5% 4 5% 6% 6% 6% 23%	1600
	21st to end	Day	19% 19% 5% 9% 7% 5% 5% 3 5% 7% 16%	1600
December	1st to 10th	Day	16% 24% 6% 14% 7% 5% 4 3 4 6% 10%	2600
	11th to 20th	Day	16% 19% 6% 12% 6% 5% 4 3 5% 6% 19%	2986
	21st to end	Day	23% 16% 5% 15% 6% 4 4 3 4 6% 15%	3960
January	1st to 10th	Night	13% 17% 8% 16% 8% 5% 4 3 4 5% 18%	6349
	11th to 20th	Night	11% 14% 8% 17% 10% 7% 6% 3 5% 5% 14%	6105
	21st to end	Night	13% 16% 7% 14% 6% 5% 4 3 5% 6% 21%	6490
February	1st to 10th	Night	12% 16% 6% 14% 8% 6% 5% 4 4 6% 19%	2600
	11th to 20th	Night	13% 15% 6% 11% 6% 5% 5% 4 4 5% 25%	2533
	21st to end	Night	14% 14% 5% 12% 5% 5% 5% 4 6% 6% 25%	2107
March	1st to 10th	Night	16% 12% 4 10% 5% 5% 4 4 5% 6% 29%	4908
	11th to 20th	Night	10% 11% 4 9% 5% 5% 5% 4 7% 7% 31%	4979
	21st to end	Night	19% 9% 4 8% 5% 4 4 4 5% 6% 33%	5467
April	1st to 10th	Night	20% 10% 3 9% 5% 4 4 4 5% 6% 29%	2020
	11th to 20th	Night	17% 8% 3 7% 5% 4 3 4 6% 7% 36%	1917
	21st to end	Night	17% 8% 4 9% 6% 4 4 4 5% 6% 34%	1800
May	1st to 10th	Night	19% 9% 3 8% 4 4 4 3 6% 6% 34%	3966
	11th to 20th	Night	12% 7% 2 6% 4 4 5% 4 6% 8% 42%	3575
	21st to end	Night	18% 7% 2 6% 4 4 4 3 5% 7% 40%	3926
June	1st to 10th	Night	14% 6% 3 6% 5% 5% 5% 4 5% 7% 40%	1600
	11th to 20th	Night	10% 6% 2 6% 4 4 4 5% 7% 9% 43%	1544
	21st to end	Night	12% 9% 3 6% 6% 4 4 4 6% 7% 40%	1400
July	1st to 10th	Night	10% 6% 2 7% 5% 5% 4 4 6% 7% 44%	3336
	11th to 20th	Night	12% 6% 2 5% 3 3 4 3 5% 8% 49%	3600
	21st to end	Night	9% 5% 2 5% 3 4 4 3 6% 9% 49%	4214
August	1st to 10th	Night	9% 6% 2 5% 4 5% 5% 3 5% 8% 47%	2915
	11th to 20th	Night	12% 7% 3 6% 3 3 3 3 5% 8% 45%	2875
	21st to end	Night	11% 6% 2 7% 4 4 5% 3 6% 9% 44%	3375
September	1st to 10th	Night	10% 5% 3 5% 4 4 5% 4 6% 8% 45%	2000
	11th to 20th	Night	11% 5% 2 5% 4 3 3 3 5% 7% 52%	2090
	21st to end	Night	16% 8% 3 6% 4 4 4 3 5% 6% 41%	2255
October	1st to 10th	Night	17% 8% 2 7% 5% 5% 4 4 5% 6% 37%	2400
	11th to 20th	Night	21% 12% 3 8% 5% 5% 5% 3 4 5% 29%	2400
	21st to end	Night	22% 11% 4 8% 5% 5% 4 4 5% 6% 26%	2640
November	1st to 10th	Night	18% 12% 3 7% 4 4 5% 3 5% 6% 32%	2674
	11th to 20th	Night	16% 17% 5% 9% 6% 5% 5% 3 6% 6% 24%	2800
	21st to end	Night	20% 16% 4 10% 6% 5% 6% 4 5% 6% 16%	2800
December	1st to 10th	Night	18% 22% 7% 13% 6% 4 4 4 5% 5% 12%	4580
	11th to 20th	Night	15% 19% 7% 16% 6% 5% 5% 4 5% 5% 14%	5208
	21st to end	Night	22% 18% 6% 16% 6% 5% 4 3 3 5% 12%	6996

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	61% 5% 11% 15% 9%	3598
	11th to 20th	Day	73% 5% 8% 9% 4	3810
	21st to end	Day	67% 6% 10% 9% 8% 1	4466
February	1st to 10th	Day	64% 5% 11% 15% 4 1	1800
	11th to 20th	Day	59% 6% 10% 15% 8% 1	1762
	21st to end	Day	62% 6% 10% 15% 7%	1518
March	1st to 10th	Day	55% 7% 13% 12% 14%	4935
	11th to 20th	Day	52% 6% 15% 18% 7% 2	4980
	21st to end	Day	51% 5% 8% 19% 15% 1	5465
April	1st to 10th	Day	54% 5% 9% 20% 11% 1	2380
	11th to 20th	Day	49% 5% 9% 21% 14% 1	2449
	21st to end	Day	51% 5% 10% 18% 13% 3	2600
May	1st to 10th	Day	48% 6% 13% 19% 10% 5%	5981
	11th to 20th	Day	46% 7% 11% 17% 18% 1	6322
	21st to end	Day	48% 6% 12% 20% 12% 2	6949
June	1st to 10th	Day	45% 7% 12% 22% 14%	2800
	11th to 20th	Day	39% 7% 15% 25% 13% 1	2847
	21st to end	Day	43% 7% 14% 23% 12% 1	3000
July	1st to 10th	Day	39% 4 15% 27% 13% 1	6530
	11th to 20th	Day	34% 4 14% 32% 15% 1	6285
	21st to end	Day	32% 5% 14% 36% 13%	6445
August	1st to 10th	Day	42% 6% 15% 26% 11% 1	4221
	11th to 20th	Day	41% 6% 16% 27% 9%	4213
	21st to end	Day	36% 5% 14% 35% 10% 1	4489
September	1st to 10th	Day	40% 7% 15% 27% 10% 1	2400
	11th to 20th	Day	35% 6% 15% 31% 13%	2307
	21st to end	Day	46% 8% 13% 24% 9%	2145
October	1st to 10th	Day	44% 5% 12% 28% 11% 1	3260
	11th to 20th	Day	48% 4 15% 22% 11%	3240
	21st to end	Day	55% 6% 14% 19% 6%	3538
November	1st to 10th	Day	53% 9% 14% 18% 7% 1	1665
	11th to 20th	Day	59% 9% 12% 13% 6% 1	1600
	21st to end	Day	65% 9% 12% 11% 3	1600
December	1st to 10th	Day	75% 4 12% 7% 1	2600
	11th to 20th	Day	68% 7% 9% 11% 5%	2986
	21st to end	Day	71% 6% 7% 9% 7%	3960
January	1st to 10th	Night	66% 5% 8% 13% 7%	6349
	11th to 20th	Night	69% 7% 9% 9% 5%	6148
	21st to end	Night	64% 6% 10% 10% 9% 1	6490
February	1st to 10th	Night	66% 6% 9% 15% 3 1	2600
	11th to 20th	Night	59% 6% 11% 17% 7%	2535
	21st to end	Night	57% 6% 13% 17% 7%	2107
March	1st to 10th	Night	55% 5% 10% 15% 12% 3	4918
	11th to 20th	Night	48% 6% 18% 19% 8% 1	4980
	21st to end	Night	50% 6% 10% 19% 14% 1	5467
April	1st to 10th	Night	56% 5% 9% 18% 11% 1	2020
	11th to 20th	Night	47% 5% 9% 22% 15% 2	1917
	21st to end	Night	51% 6% 12% 14% 16% 2	1800
May	1st to 10th	Night	49% 5% 13% 14% 15% 5%	3973
	11th to 20th	Night	39% 7% 14% 21% 17% 2	3576
	21st to end	Night	44% 6% 12% 24% 13% 1	3927
June	1st to 10th	Night	42% 7% 12% 23% 15% 2	1600
	11th to 20th	Night	36% 6% 14% 23% 20% 1	1544
	21st to end	Night	43% 6% 13% 23% 14% 1	1400
July	1st to 10th	Night	40% 3 16% 24% 16% 1	3297
	11th to 20th	Night	35% 4 12% 31% 18%	3552
	21st to end	Night	33% 5% 10% 35% 16% 1	4089
August	1st to 10th	Night	36% 5% 16% 25% 17% 1	2904
	11th to 20th	Night	37% 5% 17% 27% 14% 1	2902
	21st to end	Night	37% 5% 11% 34% 12% 1	3375
September	1st to 10th	Night	35% 8% 15% 29% 12% 1	2000
	11th to 20th	Night	32% 6% 13% 33% 16% 1	2090
	21st to end	Night	43% 6% 12% 27% 11%	2255
October	1st to 10th	Night	37% 5% 10% 28% 19%	3920
	11th to 20th	Night	47% 5% 15% 23% 9%	3899
	21st to end	Night	50% 6% 13% 23% 7%	4252
November	1st to 10th	Night	51% 7% 13% 20% 8%	2674
	11th to 20th	Night	59% 8% 12% 14% 6% 1	2800
	21st to end	Night	65% 9% 13% 10% 2	2800
December	1st to 10th	Night	73% 5% 13% 7% 2	4580
	11th to 20th	Night	73% 6% 9% 10% 3	5208
	21st to end	Night	75% 4 7% 8% 5%	6996

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	18% 20% 38% 15% 10% 1	200
	11th to 20th	Day	19% 17% 37% 19% 7% 1	247
	21st to end	Day	23% 16% 32% 22% 7%	330
February	1st to 10th	Day	22% 21% 36% 15% 5%	300
	11th to 20th	Day	19% 21% 38% 19% 3	300
	21st to end	Day	26% 22% 27% 25%	272
March	1st to 10th	Day	21% 12% 39% 24% 4	500
	11th to 20th	Day	18% 17% 35% 23% 6%	500
	21st to end	Day	28% 10% 33% 21% 8% 1	550
April	1st to 10th	Day	22% 12% 35% 22% 8% 1	500
	11th to 20th	Day	27% 13% 25% 20% 11% 3	492
	21st to end	Day	22% 13% 28% 25% 9% 2	500
May	1st to 10th	Day	21% 8% 28% 26% 12% 4	503
	11th to 20th	Day	18% 5% 27% 29% 17% 4	527
	21st to end	Day	18% 6% 24% 29% 16% 6%	573
June	1st to 10th	Day	19% 8% 26% 31% 14% 2	530
	11th to 20th	Day	16% 7% 24% 33% 16% 5%	577
	21st to end	Day	17% 7% 26% 34% 13% 3	730
July	1st to 10th	Day	10% 5% 22% 36% 21% 5%	635
	11th to 20th	Day	13% 5% 21% 31% 23% 7%	524
	21st to end	Day	8% 3 25% 37% 19% 7%	576
August	1st to 10th	Day	12% 4 18% 34% 25% 7%	526
	11th to 20th	Day	13% 3 18% 30% 27% 8%	519
	21st to end	Day	12% 5% 23% 30% 22% 7%	583
September	1st to 10th	Day	12% 9% 22% 27% 21% 9%	530
	11th to 20th	Day	10% 3 18% 27% 26% 15%	530
	21st to end	Day	16% 9% 25% 26% 18% 5%	530
October	1st to 10th	Day	19% 10% 28% 22% 15% 6%	530
	11th to 20th	Day	24% 16% 32% 20% 7% 2	530
	21st to end	Day	29% 15% 31% 20% 6%	583
November	1st to 10th	Day	25% 16% 26% 25% 8%	268
	11th to 20th	Day	22% 22% 34% 17% 5% 2	200
	21st to end	Day	25% 21% 37% 15% 2	200
December	1st to 10th	Day	25% 20% 33% 20% 3 1	200
	11th to 20th	Day	26% 25% 31% 15% 3 1	200
	21st to end	Day	27% 17% 38% 14% 4	220
January	1st to 10th	Night	23% 15% 37% 19% 6% 1	800
	11th to 20th	Night	26% 12% 33% 23% 6% 1	800
	21st to end	Night	21% 10% 33% 29% 7% 1	880
February	1st to 10th	Night	20% 11% 39% 27% 3	800
	11th to 20th	Night	20% 11% 38% 26% 4 1	783
	21st to end	Night	20% 13% 37% 25% 4	660
March	1st to 10th	Night	20% 12% 37% 27% 5%	800
	11th to 20th	Night	16% 13% 39% 27% 5% 1	800
	21st to end	Night	21% 8% 32% 29% 10%	880
April	1st to 10th	Night	25% 9% 33% 27% 6%	800
	11th to 20th	Night	20% 10% 30% 28% 10% 1	733
	21st to end	Night	20% 8% 31% 31% 11%	600
May	1st to 10th	Night	23% 2 24% 34% 15% 2	565
	11th to 20th	Night	14% 6% 28% 39% 12% 1	394
	21st to end	Night	13% 5% 22% 40% 19%	433
June	1st to 10th	Night	17% 4 30% 36% 13% 1	400
	11th to 20th	Night	11% 6% 26% 41% 15% 1	400
	21st to end	Night	16% 5% 22% 38% 18% 1	400
July	1st to 10th	Night	7% 4 20% 46% 22% 1	390
	11th to 20th	Night	11% 5% 21% 38% 24% 1	388
	21st to end	Night	11% 2 20% 45% 22% 1	560
August	1st to 10th	Night	10% 3 17% 38% 30% 2	597
	11th to 20th	Night	9% 2 20% 36% 30% 3	594
	21st to end	Night	13% 3 22% 34% 25% 2	747
September	1st to 10th	Night	12% 5% 25% 33% 21% 5%	800
	11th to 20th	Night	13% 4 19% 33% 25% 7%	800
	21st to end	Night	19% 8% 19% 31% 18% 5%	800
October	1st to 10th	Night	19% 8% 29% 27% 16% 2	800
	11th to 20th	Night	24% 13% 31% 23% 8% 1	800
	21st to end	Night	29% 12% 32% 24% 4	880
November	1st to 10th	Night	24% 12% 29% 24% 10%	789
	11th to 20th	Night	25% 15% 35% 19% 6% 1	800
	21st to end	Night	28% 15% 31% 22% 4	800
December	1st to 10th	Night	30% 17% 33% 16% 4	800
	11th to 20th	Night	23% 16% 38% 18% 4 1	800
	21st to end	Night	29% 13% 34% 21% 2	880

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