Farmington
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Farmington clear sky chart from 2005-11-06 to 2026-05-17.

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	11% 7% 3 6% 4 4 4 4 6% 7% 43%	131868
	Night	12% 8% 3 7% 4 4 4 3 5% 6% 44%	131210
Transparency	Day	39% 4 11% 26% 17% 3	135463
	Night	39% 4 11% 24% 19% 3	135694
Seeing	Day	17% 13% 29% 24% 13% 4	17570
	Night	17% 13% 30% 26% 12% 1	27470

By Month

Percentage Cloud Cover SE (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% 10% 4 11% 5% 4 4 3 5% 5% 38%	4691
	11th to 20th	Day	7% 8% 3 7% 4 4 4 3 5% 6% 49%	5227
	21st to end	Day	16% 8% 4 8% 4 4 3 3 5% 5% 41%	5812
February	1st to 10th	Day	15% 10% 4 8% 6% 4 4 3 4 5% 39%	1897
	11th to 20th	Day	15% 9% 3 8% 4 3 4 3 5% 7% 38%	2048
	21st to end	Day	12% 11% 3 6% 5% 4 4 4 6% 5% 40%	1730
March	1st to 10th	Day	14% 12% 3 6% 3 3 3 2 4 5% 45%	4669
	11th to 20th	Day	10% 7% 2 4 3 3 4 3 5% 6% 53%	5090
	21st to end	Day	12% 8% 3 7% 4 5% 4 4 6% 8% 39%	5882
April	1st to 10th	Day	11% 6% 2 6% 4 4 4 4 6% 8% 44%	2520
	11th to 20th	Day	15% 8% 3 7% 5% 4 4 3 5% 7% 40%	2494
	21st to end	Day	16% 8% 2 7% 4 5% 4 3 6% 7% 38%	2520
May	1st to 10th	Day	14% 8% 3 8% 5% 5% 6% 4 7% 9% 30%	5572
	11th to 20th	Day	16% 8% 3 7% 5% 5% 5% 4 6% 8% 35%	6232
	21st to end	Day	14% 7% 2 6% 4 4 4 4 5% 7% 41%	6935
June	1st to 10th	Day	10% 5% 2 6% 5% 5% 5% 3 7% 9% 45%	2800
	11th to 20th	Day	6% 4 1 5% 5% 5% 5% 4 7% 9% 49%	2800
	21st to end	Day	4 4 1 4 4 5% 6% 5% 8% 10% 49%	2800
July	1st to 10th	Day	11% 4 2 6% 4 4 5% 4 6% 9% 46%	6360
	11th to 20th	Day	5% 4 2 6% 5% 5% 6% 5% 8% 11% 42%	6360
	21st to end	Day	6% 5% 2 6% 5% 5% 6% 6% 8% 10% 40%	6468
August	1st to 10th	Day	5% 4 1 5% 3 4 5% 4 7% 10% 53%	4169
	11th to 20th	Day	11% 6% 2 5% 4 4 4 5% 5% 8% 45%	3849
	21st to end	Day	7% 5% 2 5% 4 4 4 4 5% 8% 53%	4312
September	1st to 10th	Day	12% 5% 2 5% 3 3 4 3 6% 9% 48%	2400
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 6% 8% 48%	2370
	21st to end	Day	11% 4 1 5% 5% 3 4 3 5% 7% 52%	2200
October	1st to 10th	Day	8% 5% 2 4 4 3 4 3 5% 6% 58%	2003
	11th to 20th	Day	12% 6% 2 4 3 3 4 3 4 6% 55%	2000
	21st to end	Day	18% 8% 2 5% 3 3 3 2 4 6% 47%	2200
November	1st to 10th	Day	11% 5% 2 5% 3 4 4 3 4 6% 53%	1857
	11th to 20th	Day	11% 8% 3 5% 4 3 3 4 5% 7% 46%	1890
	21st to end	Day	15% 10% 3 5% 4 4 3 3 5% 5% 43%	1863
December	1st to 10th	Day	9% 10% 2 5% 3 3 3 3 4 5% 51%	2690
	11th to 20th	Day	13% 10% 4 7% 4 4 3 2 5% 6% 41%	3088
	21st to end	Day	19% 16% 5% 8% 5% 4 4 3 4 5% 27%	4070
January	1st to 10th	Night	13% 10% 4 10% 5% 4 4 3 4 5% 37%	8232
	11th to 20th	Night	9% 9% 3 9% 4 5% 4 3 4 5% 45%	7758
	21st to end	Night	16% 9% 4 7% 5% 4 3 3 4 5% 39%	8402
February	1st to 10th	Night	16% 11% 4 8% 4 3 3 3 5% 6% 36%	2720
	11th to 20th	Night	15% 8% 3 9% 4 4 3 3 5% 5% 42%	2458
	21st to end	Night	14% 8% 3 7% 5% 4 3 3 5% 5% 42%	2076
March	1st to 10th	Night	16% 12% 2 7% 5% 4 4 2 4 5% 40%	5449
	11th to 20th	Night	10% 9% 2 6% 3 3 4 3 5% 6% 48%	5090
	21st to end	Night	14% 8% 3 6% 5% 5% 4 4 6% 7% 39%	5289
April	1st to 10th	Night	11% 5% 2 5% 3 4 4 4 7% 7% 49%	2100
	11th to 20th	Night	14% 7% 2 6% 4 3 5% 4 6% 6% 44%	2075
	21st to end	Night	18% 6% 3 6% 4 4 4 4 4 5% 41%	2100
May	1st to 10th	Night	16% 9% 3 7% 5% 5% 4 4 6% 8% 34%	4526
	11th to 20th	Night	13% 8% 3 6% 4 4 4 3 6% 8% 41%	3793
	21st to end	Night	15% 7% 3 7% 5% 5% 4 4 6% 7% 38%	3942
June	1st to 10th	Night	9% 6% 2 5% 4 5% 5% 4 6% 8% 48%	1600
	11th to 20th	Night	6% 5% 2 4 3 4 4 4 6% 9% 55%	1600
	21st to end	Night	3 3 1 3 4 4 5% 4 8% 9% 57%	1600
July	1st to 10th	Night	10% 5% 2 5% 3 3 4 4 6% 8% 50%	3618
	11th to 20th	Night	6% 5% 2 5% 5% 4 4 3 7% 8% 50%	3617
	21st to end	Night	6% 5% 2 5% 4 4 5% 4 7% 11% 46%	4398
August	1st to 10th	Night	5% 4 2 4 3 3 4 3 5% 8% 60%	2985
	11th to 20th	Night	9% 4 2 6% 3 4 5% 3 6% 9% 48%	3200
	21st to end	Night	5% 4 2 5% 3 3 4 3 5% 9% 59%	3586
September	1st to 10th	Night	11% 5% 2 5% 3 3 4 3 4 7% 53%	2000
	11th to 20th	Night	8% 4 2 6% 3 4 4 3 5% 7% 54%	2008
	21st to end	Night	10% 5% 2 5% 4 3 4 3 6% 7% 53%	2200
October	1st to 10th	Night	6% 4 1 4 3 3 3 2 4 6% 64%	2393
	11th to 20th	Night	13% 5% 1 4 3 3 3 3 4 5% 56%	2400
	21st to end	Night	18% 8% 2 4 3 2 3 3 4 5% 47%	2640
November	1st to 10th	Night	9% 5% 2 5% 3 3 3 2 4 6% 57%	2661
	11th to 20th	Night	12% 7% 2 5% 3 3 4 3 4 6% 51%	2730
	21st to end	Night	17% 9% 3 6% 3 2 3 2 4 6% 45%	2755
December	1st to 10th	Night	13% 9% 3 8% 3 3 3 3 4 6% 47%	4720
	11th to 20th	Night	12% 9% 4 7% 4 4 4 3 5% 6% 43%	5339
	21st to end	Night	20% 14% 4 9% 5% 4 4 3 5% 5% 27%	7150

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	48% 2 11% 26% 11% 2	4692
	11th to 20th	Day	36% 2 7% 29% 19% 6%	5227
	21st to end	Day	46% 2 9% 19% 15% 8%	5812
February	1st to 10th	Day	50% 2 11% 23% 13% 1	1897
	11th to 20th	Day	46% 4 11% 20% 14% 5%	2058
	21st to end	Day	44% 4 8% 24% 14% 6%	1730
March	1st to 10th	Day	45% 3 5% 21% 18% 9%	4669
	11th to 20th	Day	32% 2 8% 28% 23% 7%	5090
	21st to end	Day	43% 3 13% 28% 11% 1	5884
April	1st to 10th	Day	39% 4 11% 25% 19% 2	2520
	11th to 20th	Day	45% 3 11% 21% 16% 4	2494
	21st to end	Day	46% 3 12% 24% 13% 1	2520
May	1st to 10th	Day	50% 4 11% 22% 12% 1	5607
	11th to 20th	Day	48% 5% 11% 23% 13% 1	6236
	21st to end	Day	43% 5% 8% 24% 18% 2	6949
June	1st to 10th	Day	35% 5% 13% 28% 17% 2	2800
	11th to 20th	Day	30% 6% 11% 28% 21% 3	2800
	21st to end	Day	28% 7% 18% 26% 17% 5%	2800
July	1st to 10th	Day	35% 5% 11% 28% 19% 2	6291
	11th to 20th	Day	32% 9% 16% 30% 11% 1	6285
	21st to end	Day	35% 8% 16% 29% 11% 1	6285
August	1st to 10th	Day	26% 6% 15% 35% 19%	4155
	11th to 20th	Day	36% 5% 13% 27% 17% 2	3885
	21st to end	Day	29% 5% 13% 34% 15% 3	4311
September	1st to 10th	Day	34% 4 12% 27% 19% 4	2400
	11th to 20th	Day	32% 5% 9% 27% 25% 2	2370
	21st to end	Day	32% 5% 7% 28% 26% 3	2200
October	1st to 10th	Day	17% 2 5% 20% 45% 10%	3263
	11th to 20th	Day	23% 3 5% 23% 37% 10%	3240
	21st to end	Day	31% 2 6% 28% 28% 4	3538
November	1st to 10th	Day	33% 3 9% 28% 20% 6%	1857
	11th to 20th	Day	38% 4 8% 23% 21% 7%	1890
	21st to end	Day	45% 3 8% 25% 18% 1	1863
December	1st to 10th	Day	36% 3 8% 36% 16% 1	2690
	11th to 20th	Day	45% 3 8% 25% 18% 2	3085
	21st to end	Day	62% 3 11% 14% 8% 2	4070
January	1st to 10th	Night	51% 2 11% 23% 11% 1	8233
	11th to 20th	Night	42% 2 6% 25% 22% 3	7758
	21st to end	Night	49% 2 9% 20% 17% 3	8402
February	1st to 10th	Night	50% 3 9% 23% 13% 2	2720
	11th to 20th	Night	46% 3 9% 22% 17% 3	2459
	21st to end	Night	44% 3 8% 23% 17% 4	2076
March	1st to 10th	Night	49% 2 6% 20% 17% 5%	5449
	11th to 20th	Night	38% 3 10% 22% 19% 8%	5090
	21st to end	Night	44% 3 14% 27% 11% 1	5289
April	1st to 10th	Night	34% 4 13% 26% 20% 3	2100
	11th to 20th	Night	41% 4 10% 23% 18% 4	2075
	21st to end	Night	45% 4 9% 25% 15% 2	2100
May	1st to 10th	Night	48% 5% 15% 20% 11% 1	4556
	11th to 20th	Night	42% 6% 13% 24% 14% 2	3794
	21st to end	Night	46% 4 10% 23% 14% 3	3950
June	1st to 10th	Night	34% 5% 13% 26% 19% 2	1600
	11th to 20th	Night	25% 4 12% 31% 23% 4	1600
	21st to end	Night	22% 5% 17% 30% 18% 7%	1600
July	1st to 10th	Night	32% 6% 12% 26% 22% 3	3580
	11th to 20th	Night	31% 7% 16% 30% 14% 2	3572
	21st to end	Night	31% 6% 21% 27% 13% 1	4271
August	1st to 10th	Night	22% 5% 19% 31% 21% 1	2975
	11th to 20th	Night	32% 6% 15% 26% 17% 3	3230
	21st to end	Night	23% 4 12% 38% 19% 3	3586
September	1st to 10th	Night	33% 4 9% 29% 19% 6%	2000
	11th to 20th	Night	31% 4 9% 29% 25% 2	2008
	21st to end	Night	32% 4 9% 23% 28% 4	2200
October	1st to 10th	Night	14% 2 6% 17% 47% 13%	3913
	11th to 20th	Night	23% 2 6% 21% 36% 12%	3899
	21st to end	Night	31% 3 7% 26% 27% 7%	4252
November	1st to 10th	Night	30% 3 11% 28% 23% 5%	2661
	11th to 20th	Night	36% 3 7% 25% 24% 6%	2730
	21st to end	Night	43% 3 8% 25% 19% 2	2755
December	1st to 10th	Night	41% 3 9% 29% 17% 1	4720
	11th to 20th	Night	42% 3 11% 22% 20% 1	5341
	21st to end	Night	59% 3 11% 18% 8% 1	7150

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	29% 22% 35% 11% 3	330
	11th to 20th	Day	27% 29% 35% 8%	330
	21st to end	Day	21% 31% 37% 10% 1	363
February	1st to 10th	Day	24% 25% 38% 12% 1	330
	11th to 20th	Day	32% 28% 31% 7% 1 1	330
	21st to end	Day	32% 24% 36% 6% 1	273
March	1st to 10th	Day	21% 28% 38% 10% 2	330
	11th to 20th	Day	32% 23% 35% 8% 2	330
	21st to end	Day	29% 21% 36% 12% 2	494
April	1st to 10th	Day	23% 21% 36% 16% 4	540
	11th to 20th	Day	26% 22% 30% 17% 4 1	532
	21st to end	Day	22% 17% 39% 17% 5% 1	540
May	1st to 10th	Day	20% 19% 37% 17% 5% 1	543
	11th to 20th	Day	19% 15% 33% 21% 9% 3	675
	21st to end	Day	13% 12% 35% 25% 12% 4	789
June	1st to 10th	Day	12% 6% 27% 29% 22% 5%	730
	11th to 20th	Day	7% 5% 26% 37% 21% 4	730
	21st to end	Day	5% 6% 31% 35% 19% 5%	730
July	1st to 10th	Day	12% 3 19% 30% 27% 10%	721
	11th to 20th	Day	5% 3 21% 40% 24% 6%	718
	21st to end	Day	9% 4 19% 35% 27% 6%	794
August	1st to 10th	Day	8% 3 19% 38% 25% 7%	687
	11th to 20th	Day	10% 4 22% 30% 27% 7%	519
	21st to end	Day	10% 3 17% 32% 28% 10%	583
September	1st to 10th	Day	11% 5% 21% 34% 24% 6%	530
	11th to 20th	Day	9% 4 18% 31% 27% 11%	530
	21st to end	Day	14% 8% 24% 26% 20% 8%	530
October	1st to 10th	Day	11% 9% 32% 33% 10% 4	333
	11th to 20th	Day	20% 15% 36% 22% 6% 1	330
	21st to end	Day	29% 21% 32% 16% 2	363
November	1st to 10th	Day	17% 15% 40% 22% 5% 1	330
	11th to 20th	Day	22% 21% 34% 17% 5% 1	330
	21st to end	Day	30% 18% 31% 15% 5% 1	330
December	1st to 10th	Day	20% 23% 37% 13% 5% 2	330
	11th to 20th	Day	26% 24% 34% 14% 2	330
	21st to end	Day	30% 22% 37% 9% 2	363
January	1st to 10th	Night	22% 23% 35% 18% 2	1050
	11th to 20th	Night	23% 28% 33% 14% 3	1050
	21st to end	Night	19% 24% 39% 17% 1	1155
February	1st to 10th	Night	24% 21% 36% 17% 1	1040
	11th to 20th	Night	23% 25% 36% 14% 2	823
	21st to end	Night	23% 23% 34% 18% 1	692
March	1st to 10th	Night	26% 18% 36% 18% 2	822
	11th to 20th	Night	22% 17% 38% 20% 3	630
	21st to end	Night	25% 17% 33% 20% 4	693
April	1st to 10th	Night	15% 20% 38% 25% 3	630
	11th to 20th	Night	20% 17% 32% 23% 7%	623
	21st to end	Night	21% 13% 37% 22% 7%	630
May	1st to 10th	Night	17% 11% 36% 28% 8%	630
	11th to 20th	Night	18% 6% 36% 27% 13% 1	609
	21st to end	Night	12% 6% 30% 33% 16% 3	650
June	1st to 10th	Night	11% 5% 22% 39% 22% 2	600
	11th to 20th	Night	8% 2 22% 46% 21% 2	600
	21st to end	Night	4 3 27% 39% 26% 2	600
July	1st to 10th	Night	9% 2 12% 36% 33% 7%	585
	11th to 20th	Night	6% 2 15% 43% 31% 4	582
	21st to end	Night	8% 1 16% 38% 33% 3	657
August	1st to 10th	Night	8% 2 14% 40% 33% 5%	597
	11th to 20th	Night	8% 1 15% 39% 34% 4	594
	21st to end	Night	7% 2 14% 37% 35% 7%	660
September	1st to 10th	Night	12% 3 16% 36% 30% 4	600
	11th to 20th	Night	10% 2 15% 35% 32% 6%	608
	21st to end	Night	12% 6% 24% 28% 25% 5%	800
October	1st to 10th	Night	8% 5% 28% 33% 22% 4	800
	11th to 20th	Night	15% 13% 32% 25% 13% 1	800
	21st to end	Night	24% 16% 33% 21% 6%	880
November	1st to 10th	Night	13% 12% 41% 25% 9%	820
	11th to 20th	Night	19% 16% 34% 25% 6%	840
	21st to end	Night	25% 18% 34% 19% 5%	865
December	1st to 10th	Night	22% 18% 36% 20% 4	1050
	11th to 20th	Night	23% 16% 37% 22% 3	1050
	21st to end	Night	26% 20% 35% 17% 2	1155

Page generated at 2026-05-14 00:58:54. Version ac07

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