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 2025-01-22.

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	12% 7% 2 6% 4 4 4 4 6% 7% 43%	104936
	Night	13% 8% 3 6% 4 4 4 3 5% 6% 45%	104520
Transparency	Day	39% 4 11% 26% 18% 3	108570
	Night	39% 3 11% 25% 18% 4	109028
Seeing	Day	17% 13% 29% 24% 13% 4	15800
	Night	17% 13% 30% 26% 12% 1	25722

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% 5% 9% 5% 4 4 4 5% 5% 37%	2607
	11th to 20th	Day	12% 9% 3 6% 4 4 4 3 5% 5% 44%	2884
	21st to end	Day	21% 11% 5% 7% 4 4 3 3 3 5% 35%	3144
February	1st to 10th	Day	15% 10% 4 7% 5% 3 4 3 4 5% 38%	1715
	11th to 20th	Day	14% 8% 3 8% 4 3 4 4 6% 8% 38%	1848
	21st to end	Day	13% 12% 3 5% 5% 4 4 5% 6% 6% 38%	1570
March	1st to 10th	Day	18% 13% 3 6% 3 3 4 2 4 4 40%	3179
	11th to 20th	Day	13% 7% 2 4 3 3 4 3 5% 5% 51%	3480
	21st to end	Day	13% 9% 3 7% 4 5% 4 4 6% 7% 37%	4023
April	1st to 10th	Day	10% 6% 2 6% 5% 4 4 4 6% 8% 46%	2280
	11th to 20th	Day	15% 8% 3 6% 5% 4 4 2 5% 6% 41%	2254
	21st to end	Day	17% 8% 2 7% 4 5% 4 3 6% 6% 38%	2280
May	1st to 10th	Day	13% 7% 3 6% 6% 5% 6% 5% 7% 10% 33%	3797
	11th to 20th	Day	18% 7% 2 6% 4 4 4 3 6% 8% 38%	4287
	21st to end	Day	10% 7% 2 6% 5% 5% 5% 4 6% 8% 42%	4824
June	1st to 10th	Day	10% 5% 2 6% 5% 5% 5% 3 7% 9% 44%	2660
	11th to 20th	Day	5% 4 1 5% 5% 5% 5% 4 7% 9% 50%	2660
	21st to end	Day	4 4 1 4 4 5% 6% 5% 8% 10% 49%	2660
July	1st to 10th	Day	13% 4 2 6% 4 4 5% 4 7% 10% 41%	4440
	11th to 20th	Day	4 3 1 5% 5% 5% 5% 5% 7% 11% 49%	4440
	21st to end	Day	7% 7% 2 8% 6% 5% 6% 6% 8% 9% 36%	4497
August	1st to 10th	Day	6% 4 1 5% 3 4 5% 4 7% 10% 52%	4041
	11th to 20th	Day	11% 6% 2 6% 4 4 4 5% 5% 8% 45%	3729
	21st to end	Day	7% 5% 2 5% 4 4 4 4 5% 8% 53%	4180
September	1st to 10th	Day	12% 5% 2 5% 3 3 4 3 6% 9% 48%	2280
	11th to 20th	Day	11% 5% 2 5% 4 4 4 4 6% 8% 47%	2252
	21st to end	Day	11% 4 1 4 5% 3 4 3 5% 7% 52%	2090
October	1st to 10th	Day	8% 5% 2 4 4 3 4 3 4 6% 58%	1903
	11th to 20th	Day	12% 6% 2 4 3 3 3 3 4 6% 54%	1900
	21st to end	Day	17% 8% 2 5% 3 3 3 2 4 6% 47%	2090
November	1st to 10th	Day	11% 5% 2 5% 3 4 4 3 4 5% 53%	1767
	11th to 20th	Day	11% 8% 3 5% 4 3 3 4 5% 7% 47%	1800
	21st to end	Day	15% 9% 3 6% 4 4 4 3 5% 5% 43%	1775
December	1st to 10th	Day	10% 10% 2 5% 4 3 3 3 4 5% 51%	2610
	11th to 20th	Day	13% 10% 4 7% 4 4 3 2 5% 6% 41%	3008
	21st to end	Day	19% 16% 5% 8% 5% 4 4 3 4 4 26%	3982
January	1st to 10th	Night	14% 9% 4 9% 4 4 4 3 5% 6% 37%	4568
	11th to 20th	Night	12% 10% 4 10% 5% 6% 5% 4 5% 5% 35%	4301
	21st to end	Night	23% 12% 5% 7% 4 3 3 3 4 4 32%	4546
February	1st to 10th	Night	17% 11% 4 8% 5% 3 3 3 5% 6% 35%	2462
	11th to 20th	Night	14% 7% 3 9% 4 4 4 2 5% 5% 43%	2218
	21st to end	Night	15% 9% 4 7% 5% 4 4 3 5% 5% 40%	1884
March	1st to 10th	Night	20% 11% 2 6% 4 4 3 2 4 4 41%	3704
	11th to 20th	Night	12% 7% 2 5% 3 3 4 3 4 6% 50%	3480
	21st to end	Night	14% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	3608
April	1st to 10th	Night	10% 5% 2 6% 4 4 4 4 6% 6% 50%	1900
	11th to 20th	Night	14% 7% 2 6% 4 4 5% 3 6% 5% 45%	1875
	21st to end	Night	19% 6% 3 6% 4 4 4 3 4 5% 42%	1900
May	1st to 10th	Night	17% 8% 2 5% 4 3 4 4 5% 8% 40%	3081
	11th to 20th	Night	15% 8% 2 5% 3 3 3 3 5% 8% 45%	2612
	21st to end	Night	9% 7% 3 8% 5% 6% 5% 4 7% 9% 39%	2743
June	1st to 10th	Night	9% 5% 1 5% 4 4 5% 4 6% 8% 48%	1520
	11th to 20th	Night	5% 4 1 3 2 4 4 4 6% 9% 57%	1520
	21st to end	Night	3 3 1 3 3 4 5% 4 8% 9% 57%	1520
July	1st to 10th	Night	11% 4 2 4 3 3 4 4 6% 8% 50%	2530
	11th to 20th	Night	6% 4 1 4 4 4 4 3 6% 8% 58%	2530
	21st to end	Night	8% 6% 2 6% 5% 5% 5% 5% 7% 9% 42%	3061
August	1st to 10th	Night	5% 3 1 4 3 3 4 3 5% 8% 60%	2893
	11th to 20th	Night	9% 4 2 6% 3 4 5% 3 6% 9% 48%	3100
	21st to end	Night	5% 4 2 5% 3 3 4 4 5% 9% 59%	3476
September	1st to 10th	Night	11% 5% 2 4 3 3 4 3 4 7% 54%	1900
	11th to 20th	Night	9% 4 2 6% 3 4 4 3 5% 7% 53%	1907
	21st to end	Night	10% 5% 2 5% 4 3 3 3 6% 7% 53%	2090
October	1st to 10th	Night	6% 3 1 4 3 3 3 3 4 6% 64%	2273
	11th to 20th	Night	13% 5% 1 4 4 3 3 3 4 5% 56%	2280
	21st to end	Night	17% 7% 2 4 3 3 3 3 4 5% 48%	2508
November	1st to 10th	Night	10% 5% 2 5% 3 2 3 2 4 6% 57%	2531
	11th to 20th	Night	13% 6% 2 5% 3 3 4 3 4 6% 50%	2600
	21st to end	Night	17% 9% 2 6% 4 2 3 2 4 6% 46%	2624
December	1st to 10th	Night	13% 8% 3 7% 3 3 3 2 4 6% 47%	4580
	11th to 20th	Night	12% 9% 4 7% 4 4 4 3 5% 6% 43%	5199
	21st to end	Night	20% 15% 4 9% 5% 4 4 3 4 5% 26%	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	49% 2 9% 28% 10% 2	2608
	11th to 20th	Day	42% 2 9% 26% 16% 4	2884
	21st to end	Day	53% 2 8% 18% 14% 4	3144
February	1st to 10th	Day	50% 2 10% 23% 13% 2	1715
	11th to 20th	Day	45% 4 12% 20% 14% 5%	1858
	21st to end	Day	45% 4 9% 24% 12% 6%	1570
March	1st to 10th	Day	50% 4 5% 21% 12% 8%	3179
	11th to 20th	Day	36% 2 10% 29% 17% 6%	3480
	21st to end	Day	46% 3 16% 21% 13% 1	4023
April	1st to 10th	Day	37% 4 11% 26% 20% 2	2280
	11th to 20th	Day	45% 3 10% 22% 16% 4	2254
	21st to end	Day	47% 3 11% 23% 14% 1	2280
May	1st to 10th	Day	47% 4 13% 23% 11% 1	3832
	11th to 20th	Day	46% 4 11% 26% 12% 1	4291
	21st to end	Day	41% 6% 9% 23% 20% 1	4837
June	1st to 10th	Day	35% 5% 14% 27% 17% 2	2660
	11th to 20th	Day	29% 6% 11% 28% 22% 3	2660
	21st to end	Day	28% 7% 17% 26% 17% 5%	2660
July	1st to 10th	Day	37% 6% 13% 28% 13% 3	4371
	11th to 20th	Day	27% 7% 14% 34% 16% 2	4365
	21st to end	Day	42% 8% 14% 26% 9% 1	4356
August	1st to 10th	Day	26% 6% 15% 34% 19%	4027
	11th to 20th	Day	37% 5% 13% 26% 17% 2	3765
	21st to end	Day	29% 5% 13% 35% 15% 3	4179
September	1st to 10th	Day	34% 4 12% 27% 19% 4	2280
	11th to 20th	Day	33% 5% 9% 26% 24% 2	2252
	21st to end	Day	31% 5% 7% 29% 25% 3	2090
October	1st to 10th	Day	17% 2 6% 20% 45% 10%	3163
	11th to 20th	Day	23% 3 5% 22% 38% 10%	3140
	21st to end	Day	31% 2 6% 28% 28% 4	3428
November	1st to 10th	Day	34% 3 10% 26% 21% 7%	1767
	11th to 20th	Day	38% 4 7% 23% 21% 7%	1800
	21st to end	Day	45% 3 8% 25% 18% 1	1775
December	1st to 10th	Day	36% 2 8% 36% 16% 1	2610
	11th to 20th	Day	45% 3 8% 24% 18% 2	3005
	21st to end	Day	63% 2 10% 14% 9% 2	3982
January	1st to 10th	Night	49% 2 9% 26% 12% 1	4568
	11th to 20th	Night	50% 2 9% 24% 13% 2	4301
	21st to end	Night	56% 2 9% 22% 11% 1	4546
February	1st to 10th	Night	51% 3 8% 22% 13% 2	2462
	11th to 20th	Night	44% 3 10% 21% 18% 3	2219
	21st to end	Night	46% 3 9% 21% 16% 5%	1884
March	1st to 10th	Night	50% 2 7% 22% 15% 4	3704
	11th to 20th	Night	37% 3 13% 23% 19% 5%	3480
	21st to end	Night	46% 3 14% 29% 8% 1	3608
April	1st to 10th	Night	34% 4 12% 26% 20% 3	1900
	11th to 20th	Night	41% 4 9% 23% 19% 5%	1875
	21st to end	Night	46% 4 8% 25% 15% 2	1900
May	1st to 10th	Night	43% 4 17% 23% 12% 1	3111
	11th to 20th	Night	40% 5% 13% 24% 16% 1	2613
	21st to end	Night	41% 4 12% 24% 17% 1	2751
June	1st to 10th	Night	33% 5% 14% 26% 20% 3	1520
	11th to 20th	Night	23% 4 13% 33% 24% 4	1520
	21st to end	Night	23% 5% 17% 30% 18% 7%	1520
July	1st to 10th	Night	33% 5% 14% 30% 15% 4	2490
	11th to 20th	Night	24% 5% 13% 36% 19% 3	2482
	21st to end	Night	37% 6% 18% 24% 13% 2	2964
August	1st to 10th	Night	22% 5% 19% 31% 21% 1	2883
	11th to 20th	Night	33% 6% 15% 25% 17% 3	3130
	21st to end	Night	23% 5% 13% 39% 18% 3	3476
September	1st to 10th	Night	33% 4 9% 29% 19% 7%	1900
	11th to 20th	Night	32% 5% 8% 28% 24% 2	1907
	21st to end	Night	31% 4 8% 25% 27% 4	2090
October	1st to 10th	Night	14% 2 6% 17% 48% 13%	3793
	11th to 20th	Night	23% 2 6% 20% 36% 13%	3779
	21st to end	Night	30% 3 7% 26% 27% 7%	4120
November	1st to 10th	Night	30% 3 10% 27% 23% 6%	2531
	11th to 20th	Night	36% 3 7% 24% 24% 6%	2600
	21st to end	Night	42% 3 8% 25% 20% 2	2624
December	1st to 10th	Night	41% 3 9% 30% 17% 1	4580
	11th to 20th	Night	43% 3 11% 22% 19% 1	5201
	21st to end	Night	60% 3 11% 17% 8% 1	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	30% 22% 34% 11% 3	300
	11th to 20th	Day	28% 28% 34% 9%	300
	21st to end	Day	22% 33% 33% 12% 1	300
February	1st to 10th	Day	26% 26% 37% 11% 1	270
	11th to 20th	Day	30% 28% 31% 9% 1 1	270
	21st to end	Day	33% 26% 33% 6%	225
March	1st to 10th	Day	21% 29% 38% 11% 1	270
	11th to 20th	Day	32% 24% 33% 8% 2	270
	21st to end	Day	30% 22% 34% 12% 2	416
April	1st to 10th	Day	22% 21% 36% 16% 4	460
	11th to 20th	Day	26% 21% 29% 19% 4 1	452
	21st to end	Day	23% 19% 37% 15% 5% 1	460
May	1st to 10th	Day	21% 19% 36% 18% 5% 1	463
	11th to 20th	Day	19% 14% 32% 21% 9% 4	602
	21st to end	Day	11% 11% 36% 25% 13% 4	734
June	1st to 10th	Day	11% 6% 27% 29% 22% 5%	680
	11th to 20th	Day	7% 5% 27% 37% 20% 4	680
	21st to end	Day	5% 7% 32% 34% 17% 5%	680
July	1st to 10th	Day	11% 3 20% 29% 27% 9%	671
	11th to 20th	Day	5% 3 21% 41% 25% 6%	668
	21st to end	Day	9% 4 20% 36% 25% 6%	739
August	1st to 10th	Day	9% 3 19% 38% 24% 7%	639
	11th to 20th	Day	11% 4 24% 31% 25% 5%	479
	21st to end	Day	10% 3 17% 31% 29% 10%	539
September	1st to 10th	Day	11% 5% 20% 34% 24% 6%	490
	11th to 20th	Day	10% 4 19% 31% 26% 10%	490
	21st to end	Day	14% 9% 24% 26% 20% 8%	490
October	1st to 10th	Day	12% 9% 33% 32% 10% 4	303
	11th to 20th	Day	20% 16% 38% 20% 6% 1	300
	21st to end	Day	27% 22% 32% 17% 3	330
November	1st to 10th	Day	17% 15% 39% 22% 5% 1	300
	11th to 20th	Day	23% 21% 32% 17% 6% 1	300
	21st to end	Day	29% 18% 33% 15% 4 1	300
December	1st to 10th	Day	20% 23% 36% 13% 6% 2	300
	11th to 20th	Day	27% 24% 33% 14% 3	300
	21st to end	Day	31% 23% 34% 9% 2	330
January	1st to 10th	Night	23% 23% 35% 17% 3	1000
	11th to 20th	Night	23% 28% 33% 14% 3	1000
	21st to end	Night	20% 25% 38% 17% 1	1051
February	1st to 10th	Night	25% 22% 35% 17% 1	942
	11th to 20th	Night	21% 25% 37% 15% 2	743
	21st to end	Night	25% 23% 33% 17% 1	628
March	1st to 10th	Night	26% 18% 36% 18% 2	744
	11th to 20th	Night	22% 16% 38% 21% 3	570
	21st to end	Night	26% 17% 33% 20% 5%	627
April	1st to 10th	Night	14% 21% 37% 25% 3	570
	11th to 20th	Night	20% 17% 30% 25% 8% 1	563
	21st to end	Night	21% 14% 37% 21% 6%	570
May	1st to 10th	Night	16% 11% 36% 27% 8% 1	570
	11th to 20th	Night	18% 6% 36% 26% 13% 1	561
	21st to end	Night	12% 6% 29% 33% 16% 3	617
June	1st to 10th	Night	10% 5% 22% 38% 23% 2	570
	11th to 20th	Night	8% 2 23% 46% 20% 1	570
	21st to end	Night	4 3 28% 39% 24% 2	570
July	1st to 10th	Night	9% 2 13% 37% 32% 7%	555
	11th to 20th	Night	6% 2 15% 43% 30% 4	552
	21st to end	Night	8% 1 17% 39% 32% 3	624
August	1st to 10th	Night	7% 1 14% 39% 34% 5%	567
	11th to 20th	Night	8% 1 16% 40% 32% 4	564
	21st to end	Night	7% 2 15% 35% 35% 7%	627
September	1st to 10th	Night	12% 3 16% 35% 29% 5%	570
	11th to 20th	Night	11% 2 16% 35% 31% 6%	577
	21st to end	Night	12% 6% 25% 28% 24% 5%	760
October	1st to 10th	Night	8% 5% 29% 32% 22% 4	760
	11th to 20th	Night	16% 13% 33% 24% 13% 1	760
	21st to end	Night	23% 16% 33% 22% 6%	836
November	1st to 10th	Night	13% 12% 41% 24% 9%	780
	11th to 20th	Night	19% 16% 33% 25% 6%	800
	21st to end	Night	24% 18% 34% 19% 5%	824
December	1st to 10th	Night	22% 18% 36% 20% 4	1000
	11th to 20th	Night	23% 16% 36% 22% 3	1000
	21st to end	Night	26% 20% 34% 17% 2	1100

Page generated at 2025-01-19 02:06:43. Version ac07

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