Warren
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Warren clear sky chart from 2005-11-06 to 2026-06-01.

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	17% 12% 5% 10% 5% 5% 4 3 5% 6% 27%	132302
	Night	17% 14% 5% 11% 6% 4 4 3 4 5% 26%	130825
Transparency	Day	57% 5% 10% 18% 9% 1	135897
	Night	59% 5% 10% 16% 9% 1	135316
Seeing	Day	27% 18% 28% 17% 8% 3	16565
	Night	26% 16% 26% 22% 9% 1	26141

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	16% 20% 9% 27% 7% 4 2 2 2 3 8%	4763
	11th to 20th	Day	10% 22% 11% 21% 10% 7% 3 1 2 2 9%	5246
	21st to end	Day	16% 15% 8% 14% 10% 10% 6% 2 3 3 11%	5780
February	1st to 10th	Day	16% 19% 6% 14% 9% 6% 4 2 2 4 17%	1890
	11th to 20th	Day	15% 16% 8% 18% 7% 5% 4 3 4 5% 17%	1843
	21st to end	Day	18% 17% 4 13% 7% 4 4 4 4 5% 21%	1673
March	1st to 10th	Day	18% 13% 8% 10% 6% 3 3 2 3 5% 29%	5042
	11th to 20th	Day	13% 17% 7% 10% 4 4 3 3 4 6% 30%	5090
	21st to end	Day	20% 13% 5% 11% 5% 4 3 3 4 5% 27%	5586
April	1st to 10th	Day	18% 17% 4 9% 4 4 4 3 5% 6% 27%	2478
	11th to 20th	Day	19% 14% 3 6% 4 4 4 3 5% 6% 30%	2499
	21st to end	Day	21% 12% 3 6% 4 4 3 3 4 6% 34%	2730
May	1st to 10th	Day	25% 11% 3 7% 5% 5% 4 3 4 6% 26%	6018
	11th to 20th	Day	22% 11% 3 8% 5% 5% 5% 4 6% 7% 25%	6259
	21st to end	Day	20% 7% 3 7% 5% 5% 5% 4 5% 7% 32%	7103
June	1st to 10th	Day	18% 8% 3 7% 5% 5% 5% 4 6% 7% 33%	2800
	11th to 20th	Day	17% 7% 3 7% 5% 5% 6% 4 7% 8% 31%	2800
	21st to end	Day	17% 7% 2 5% 5% 5% 5% 4 6% 9% 36%	2800
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 10% 37%	6360
	11th to 20th	Day	12% 7% 3 8% 5% 5% 5% 4 7% 10% 32%	6184
	21st to end	Day	12% 6% 2 7% 4 5% 5% 4 5% 7% 42%	6424
August	1st to 10th	Day	18% 7% 3 8% 5% 6% 5% 4 7% 8% 28%	4234
	11th to 20th	Day	16% 7% 2 8% 5% 6% 6% 6% 8% 9% 26%	4174
	21st to end	Day	14% 6% 2 6% 5% 5% 6% 5% 7% 10% 35%	4416
September	1st to 10th	Day	19% 8% 2 6% 4 4 4 3 5% 6% 39%	2400
	11th to 20th	Day	14% 6% 2 7% 4 4 5% 3 7% 9% 39%	2290
	21st to end	Day	20% 8% 4 9% 5% 4 5% 4 5% 7% 30%	2150
October	1st to 10th	Day	19% 8% 3 6% 4 5% 5% 4 6% 6% 35%	2000
	11th to 20th	Day	22% 10% 3 7% 5% 5% 4 3 5% 6% 29%	2000
	21st to end	Day	25% 14% 3 8% 5% 4 4 3 5% 6% 24%	2200
November	1st to 10th	Day	15% 14% 4 8% 5% 4 4 3 5% 7% 31%	1916
	11th to 20th	Day	17% 21% 5% 9% 4 3 4 4 5% 6% 22%	1680
	21st to end	Day	21% 23% 6% 9% 5% 4 3 3 4 6% 17%	1680
December	1st to 10th	Day	19% 25% 15% 16% 4 3 2 2 3 3 8%	2680
	11th to 20th	Day	19% 22% 9% 13% 7% 4 3 2 3 3 15%	3066
	21st to end	Day	22% 25% 8% 12% 5% 4 4 2 3 4 12%	4048
January	1st to 10th	Night	14% 20% 9% 28% 9% 4 3 2 2 2 6%	8116
	11th to 20th	Night	10% 20% 11% 23% 10% 6% 4 2 3 3 7%	7639
	21st to end	Night	16% 17% 7% 15% 9% 8% 8% 3 3 3 12%	8401
February	1st to 10th	Night	17% 20% 7% 13% 8% 6% 3 3 3 3 18%	2730
	11th to 20th	Night	15% 16% 7% 17% 8% 5% 5% 3 4 4 15%	2663
	21st to end	Night	19% 15% 5% 16% 6% 4 3 3 4 4 20%	2126
March	1st to 10th	Night	19% 16% 6% 10% 8% 3 2 2 3 5% 25%	5018
	11th to 20th	Night	15% 15% 6% 7% 4 3 3 3 4 6% 35%	5089
	21st to end	Night	17% 14% 6% 11% 5% 4 3 3 4 5% 29%	5588
April	1st to 10th	Night	19% 16% 4 8% 4 3 4 3 5% 6% 27%	2140
	11th to 20th	Night	20% 13% 3 5% 4 4 4 4 4 6% 34%	2075
	21st to end	Night	16% 12% 3 7% 4 5% 4 3 5% 8% 33%	1903
May	1st to 10th	Night	27% 12% 3 6% 4 3 4 3 4 5% 27%	4143
	11th to 20th	Night	21% 12% 3 7% 4 3 4 3 4 5% 33%	3850
	21st to end	Night	22% 9% 2 6% 3 3 4 3 5% 8% 35%	4014
June	1st to 10th	Night	14% 7% 2 7% 5% 5% 3 5% 6% 8% 38%	1600
	11th to 20th	Night	14% 8% 2 6% 4 4 4 4 6% 10% 38%	1600
	21st to end	Night	15% 6% 2 5% 4 4 4 3 5% 9% 41%	1600
July	1st to 10th	Night	14% 8% 3 6% 4 4 4 3 5% 8% 40%	3600
	11th to 20th	Night	13% 7% 3 7% 4 5% 4 4 6% 9% 38%	3773
	21st to end	Night	11% 6% 2 5% 4 4 5% 4 5% 8% 46%	4428
August	1st to 10th	Night	15% 8% 3 7% 5% 5% 5% 4 6% 7% 36%	2915
	11th to 20th	Night	18% 7% 2 6% 4 4 4 4 6% 7% 37%	2875
	21st to end	Night	11% 7% 2 6% 4 4 4 4 6% 9% 44%	3449
September	1st to 10th	Night	14% 7% 2 6% 4 4 4 3 5% 7% 45%	2000
	11th to 20th	Night	12% 6% 3 5% 4 3 3 4 5% 7% 49%	2105
	21st to end	Night	19% 9% 4 7% 4 4 5% 3 5% 6% 33%	2250
October	1st to 10th	Night	17% 7% 2 6% 4 4 5% 3 4 7% 40%	2400
	11th to 20th	Night	21% 10% 3 7% 4 3 4 4 6% 6% 33%	2400
	21st to end	Night	27% 12% 2 6% 4 4 4 3 4 5% 29%	2640
November	1st to 10th	Night	15% 15% 3 7% 4 3 3 4 5% 7% 36%	2597
	11th to 20th	Night	18% 20% 4 8% 4 4 5% 3 5% 5% 23%	2940
	21st to end	Night	19% 20% 7% 10% 5% 3 4 2 5% 5% 19%	2940
December	1st to 10th	Night	16% 25% 12% 15% 5% 4 4 3 3 3 10%	4720
	11th to 20th	Night	21% 21% 9% 13% 5% 3 3 2 3 3 16%	5348
	21st to end	Night	21% 21% 8% 13% 7% 4 4 3 4 4 13%	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	83% 3 6% 6% 2	4764
	11th to 20th	Day	84% 2 4 7% 2	5280
	21st to end	Day	79% 4 7% 8% 3	5780
February	1st to 10th	Day	74% 3 7% 11% 5%	1890
	11th to 20th	Day	71% 4 7% 12% 5%	1852
	21st to end	Day	64% 5% 10% 14% 5% 2	1673
March	1st to 10th	Day	60% 3 11% 20% 6%	5045
	11th to 20th	Day	56% 4 15% 18% 6% 1	5090
	21st to end	Day	59% 4 6% 19% 11% 1	5586
April	1st to 10th	Day	58% 4 10% 16% 11% 1	2478
	11th to 20th	Day	54% 6% 9% 18% 11% 2	2499
	21st to end	Day	53% 5% 10% 19% 12% 2	2730
May	1st to 10th	Day	59% 5% 7% 18% 8% 3	6027
	11th to 20th	Day	56% 7% 9% 18% 9% 1	6263
	21st to end	Day	50% 7% 10% 19% 12% 2	7103
June	1st to 10th	Day	47% 7% 12% 20% 14% 1	2800
	11th to 20th	Day	47% 8% 13% 20% 11% 1	2800
	21st to end	Day	45% 6% 14% 23% 13%	2800
July	1st to 10th	Day	40% 7% 13% 25% 15% 1	6290
	11th to 20th	Day	44% 7% 13% 21% 15%	6109
	21st to end	Day	40% 7% 10% 25% 17% 1	6240
August	1st to 10th	Day	49% 8% 14% 21% 8%	4221
	11th to 20th	Day	48% 10% 14% 21% 7% 1	4213
	21st to end	Day	41% 7% 12% 28% 11% 1	4416
September	1st to 10th	Day	45% 6% 11% 22% 15% 1	2400
	11th to 20th	Day	41% 6% 12% 26% 14% 1	2290
	21st to end	Day	53% 6% 10% 20% 10% 1	2150
October	1st to 10th	Day	42% 6% 12% 23% 16% 1	3260
	11th to 20th	Day	49% 5% 13% 16% 13% 4	3240
	21st to end	Day	49% 5% 14% 22% 10% 1	3538
November	1st to 10th	Day	52% 7% 11% 17% 12% 2	1916
	11th to 20th	Day	62% 5% 11% 14% 6% 2	1680
	21st to end	Day	70% 4 11% 11% 4 1	1680
December	1st to 10th	Day	83% 3 7% 6% 1	2680
	11th to 20th	Day	74% 4 9% 11% 2	3066
	21st to end	Day	78% 4 9% 7% 2	4048
January	1st to 10th	Night	85% 3 4 6% 1	8116
	11th to 20th	Night	84% 3 7% 5% 2	7680
	21st to end	Night	78% 4 7% 8% 3	8401
February	1st to 10th	Night	73% 4 6% 12% 5%	2730
	11th to 20th	Night	72% 5% 8% 11% 4	2665
	21st to end	Night	68% 4 8% 12% 7% 1	2126
March	1st to 10th	Night	63% 3 11% 17% 5%	5028
	11th to 20th	Night	51% 5% 15% 20% 7% 3	5090
	21st to end	Night	57% 4 8% 15% 14% 2	5588
April	1st to 10th	Night	58% 4 11% 16% 10% 1	2140
	11th to 20th	Night	51% 6% 11% 18% 12% 2	2075
	21st to end	Night	49% 5% 11% 22% 11% 2	1903
May	1st to 10th	Night	58% 5% 8% 15% 11% 3	4150
	11th to 20th	Night	53% 6% 11% 19% 10% 1	3851
	21st to end	Night	47% 6% 10% 21% 12% 3	4015
June	1st to 10th	Night	42% 7% 12% 23% 14% 2	1600
	11th to 20th	Night	42% 7% 14% 22% 14% 2	1600
	21st to end	Night	39% 8% 14% 23% 15% 1	1600
July	1st to 10th	Night	42% 6% 10% 26% 15% 1	3560
	11th to 20th	Night	40% 7% 15% 26% 12% 1	3725
	21st to end	Night	35% 7% 12% 22% 23%	4297
August	1st to 10th	Night	45% 7% 12% 25% 10% 1	2904
	11th to 20th	Night	43% 7% 15% 27% 8%	2902
	21st to end	Night	35% 7% 15% 32% 10% 1	3449
September	1st to 10th	Night	39% 6% 12% 26% 15% 3	2000
	11th to 20th	Night	35% 5% 13% 28% 18% 1	2105
	21st to end	Night	51% 6% 12% 18% 12% 1	2250
October	1st to 10th	Night	42% 5% 10% 22% 20% 1	3920
	11th to 20th	Night	46% 5% 12% 17% 14% 5%	3899
	21st to end	Night	43% 4 15% 24% 13% 1	4252
November	1st to 10th	Night	48% 5% 11% 21% 11% 3	2597
	11th to 20th	Night	62% 5% 10% 14% 6% 3	2940
	21st to end	Night	67% 5% 10% 14% 3 1	2940
December	1st to 10th	Night	79% 5% 8% 6% 2	4720
	11th to 20th	Night	74% 3 9% 12% 3	5348
	21st to end	Night	76% 5% 8% 10% 2	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	37% 28% 26% 7% 2	239
	11th to 20th	Day	40% 32% 21% 5% 2	330
	21st to end	Day	37% 28% 26% 8% 1	363
February	1st to 10th	Day	35% 27% 30% 7% 1	330
	11th to 20th	Day	40% 26% 29% 4	330
	21st to end	Day	40% 26% 28% 5%	336
March	1st to 10th	Day	32% 26% 30% 10% 2	540
	11th to 20th	Day	36% 21% 31% 9% 2 1	540
	21st to end	Day	37% 22% 25% 12% 3 1	594
April	1st to 10th	Day	33% 24% 26% 12% 4 1	540
	11th to 20th	Day	35% 21% 25% 11% 7% 2	532
	21st to end	Day	30% 19% 33% 14% 3 1	540
May	1st to 10th	Day	32% 22% 25% 13% 6% 1	543
	11th to 20th	Day	27% 15% 30% 20% 7% 2	567
	21st to end	Day	22% 14% 27% 21% 12% 4	617
June	1st to 10th	Day	22% 16% 29% 22% 8% 2	530
	11th to 20th	Day	21% 15% 27% 24% 11% 2	530
	21st to end	Day	19% 12% 35% 23% 7% 3	530
July	1st to 10th	Day	13% 9% 29% 25% 18% 6%	525
	11th to 20th	Day	15% 10% 29% 25% 15% 6%	524
	21st to end	Day	14% 11% 30% 27% 14% 5%	576
August	1st to 10th	Day	13% 10% 26% 25% 19% 7%	526
	11th to 20th	Day	17% 9% 24% 26% 14% 9%	519
	21st to end	Day	17% 9% 28% 24% 15% 7%	583
September	1st to 10th	Day	21% 14% 19% 22% 16% 7%	530
	11th to 20th	Day	14% 4 23% 26% 24% 9%	530
	21st to end	Day	25% 12% 27% 19% 13% 3	530
October	1st to 10th	Day	20% 13% 29% 18% 15% 4	530
	11th to 20th	Day	28% 20% 30% 14% 5% 2	530
	21st to end	Day	36% 18% 28% 15% 4	583
November	1st to 10th	Day	30% 21% 28% 15% 5% 2	426
	11th to 20th	Day	41% 19% 29% 6% 4 1	220
	21st to end	Day	40% 22% 31% 7%	220
December	1st to 10th	Day	38% 28% 25% 5% 2 1	220
	11th to 20th	Day	39% 25% 29% 6% 1	220
	21st to end	Day	41% 25% 27% 7% 1	242
January	1st to 10th	Night	31% 25% 32% 9% 3	840
	11th to 20th	Night	32% 27% 26% 13% 2	840
	21st to end	Night	29% 27% 29% 13% 2	924
February	1st to 10th	Night	33% 20% 30% 16%	840
	11th to 20th	Night	30% 26% 32% 11% 1	823
	21st to end	Night	31% 26% 27% 14% 2	692
March	1st to 10th	Night	30% 22% 30% 16% 2	840
	11th to 20th	Night	33% 20% 24% 18% 5%	840
	21st to end	Night	28% 20% 31% 16% 4 1	924
April	1st to 10th	Night	30% 17% 31% 18% 4	840
	11th to 20th	Night	29% 16% 29% 18% 8% 1	831
	21st to end	Night	23% 12% 32% 29% 4 1	643
May	1st to 10th	Night	26% 11% 25% 28% 10%	630
	11th to 20th	Night	20% 11% 30% 32% 7%	505
	21st to end	Night	17% 7% 29% 28% 18% 2	455
June	1st to 10th	Night	16% 4 31% 35% 14% 1	400
	11th to 20th	Night	15% 9% 27% 37% 12%	400
	21st to end	Night	16% 7% 30% 35% 14%	400
July	1st to 10th	Night	12% 4 23% 38% 20% 3	390
	11th to 20th	Night	12% 4 19% 39% 23% 2	457
	21st to end	Night	13% 5% 19% 39% 23% 1	657
August	1st to 10th	Night	12% 4 18% 38% 27% 2	597
	11th to 20th	Night	16% 4 17% 30% 30% 3	594
	21st to end	Night	14% 5% 19% 33% 26% 3	795
September	1st to 10th	Night	18% 7% 22% 29% 21% 3	800
	11th to 20th	Night	13% 7% 18% 31% 28% 4	800
	21st to end	Night	24% 11% 21% 25% 16% 3	800
October	1st to 10th	Night	21% 9% 24% 26% 18% 2	800
	11th to 20th	Night	27% 14% 30% 21% 8% 1	800
	21st to end	Night	35% 13% 28% 20% 4	880
November	1st to 10th	Night	24% 16% 29% 24% 7%	820
	11th to 20th	Night	32% 17% 29% 16% 4 1	840
	21st to end	Night	33% 22% 27% 14% 4	840
December	1st to 10th	Night	36% 24% 25% 12% 3	840
	11th to 20th	Night	34% 24% 25% 14% 3	840
	21st to end	Night	32% 24% 28% 14% 1	924

Page generated at 2026-05-29 01:53:28. Version ac07

Copyright © 2026 Attilla Danko.