21200 W Road And I-84
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the 21200 W Road And I-84 clear sky chart from 2005-11-06 to 2024-11-05.

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	6% 8% 2 6% 4 4 4 3 5% 7% 51%	105189
	Night	7% 8% 3 7% 4 4 4 3 5% 6% 49%	102528
Transparency	Day	31% 5% 10% 19% 20% 14%	104942
	Night	35% 5% 11% 19% 18% 12%	102363
Seeing	Day	9% 6% 20% 32% 24% 9%	15015
	Night	11% 4 17% 39% 25% 4	24820

By Month

Percentage Cloud Cover SW (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	8% 17% 7% 13% 6% 7% 4 3 4 4 25%	2539
	11th to 20th	Day	8% 21% 5% 11% 7% 6% 4 4 5% 5% 24%	2794
	21st to end	Day	10% 20% 6% 12% 8% 6% 5% 3 4 6% 21%	3146
February	1st to 10th	Day	11% 15% 5% 10% 6% 4 3 4 6% 7% 30%	1710
	11th to 20th	Day	11% 14% 4 9% 5% 4 4 4 5% 7% 34%	1744
	21st to end	Day	6% 13% 5% 8% 5% 6% 6% 5% 7% 6% 33%	1570
March	1st to 10th	Day	6% 15% 5% 9% 5% 5% 4 4 5% 6% 37%	3284
	11th to 20th	Day	6% 9% 3 6% 4 3 4 3 5% 6% 50%	3490
	21st to end	Day	9% 14% 4 10% 6% 6% 6% 5% 7% 9% 25%	3825
April	1st to 10th	Day	10% 10% 4 7% 4 4 4 3 5% 6% 42%	2123
	11th to 20th	Day	8% 9% 3 6% 5% 5% 4 4 6% 7% 44%	2437
	21st to end	Day	8% 8% 2 7% 5% 4 4 4 6% 8% 44%	2470
May	1st to 10th	Day	6% 10% 3 7% 5% 4 6% 4 6% 7% 42%	4110
	11th to 20th	Day	4 3 1 4 4 4 4 4 6% 9% 57%	4071
	21st to end	Day	6% 6% 2 6% 5% 5% 4 4 6% 7% 51%	4477
June	1st to 10th	Day	5% 4 2 4 4 4 5% 4 6% 9% 53%	2631
	11th to 20th	Day	6% 5% 2 4 3 3 4 3 5% 8% 58%	2850
	21st to end	Day	2 3 1 3 2 3 2 3 4 6% 71%	2749
July	1st to 10th	Day	1 1 1 2 2 1 2 3 4 5% 77%	4420
	11th to 20th	Day	2 3 1 4 2 3 4 4 7% 7% 63%	4270
	21st to end	Day	4 2 1 3 2 3 3 4 6% 7% 66%	4454
August	1st to 10th	Day	3 3 1 4 3 3 3 3 5% 7% 66%	4092
	11th to 20th	Day	3 2 1 3 2 3 3 3 5% 7% 69%	4028
	21st to end	Day	3 2 1 2 2 2 2 2 4 5% 74%	4521
September	1st to 10th	Day	4 3 1 3 3 3 3 3 5% 4 68%	2143
	11th to 20th	Day	4 4 1 4 3 3 3 4 4 6% 65%	2090
	21st to end	Day	7% 3 1 3 2 2 2 3 3 5% 69%	2090
October	1st to 10th	Day	6% 3 1 4 2 3 3 2 4 5% 68%	3370
	11th to 20th	Day	4 5% 2 4 3 3 3 3 5% 7% 61%	3150
	21st to end	Day	5% 6% 2 5% 3 3 4 3 5% 7% 58%	3296
November	1st to 10th	Day	10% 11% 3 6% 5% 4 4 3 5% 6% 43%	1710
	11th to 20th	Day	12% 8% 2 5% 3 3 4 4 5% 7% 48%	1710
	21st to end	Day	8% 12% 4 8% 4 5% 3 3 5% 7% 42%	1558
December	1st to 10th	Day	11% 13% 4 9% 6% 5% 4 3 4 5% 35%	1520
	11th to 20th	Day	12% 13% 4 11% 7% 7% 6% 4 6% 7% 24%	1926
	21st to end	Day	8% 12% 5% 12% 5% 4 5% 5% 6% 6% 31%	2821
January	1st to 10th	Night	8% 14% 4 9% 5% 4 4 4 6% 8% 34%	4406
	11th to 20th	Night	10% 18% 5% 11% 5% 4 4 4 5% 7% 26%	4167
	21st to end	Night	10% 18% 4 11% 6% 5% 5% 3 6% 6% 25%	4521
February	1st to 10th	Night	10% 16% 5% 9% 4 4 4 4 6% 5% 33%	2470
	11th to 20th	Night	10% 12% 3 8% 5% 4 4 3 5% 6% 42%	2318
	21st to end	Night	7% 14% 4 8% 6% 4 4 4 6% 6% 38%	1884
March	1st to 10th	Night	7% 14% 4 8% 5% 4 5% 4 6% 7% 37%	3589
	11th to 20th	Night	4 7% 2 6% 4 4 5% 4 6% 7% 50%	3490
	21st to end	Night	8% 11% 4 9% 6% 5% 5% 4 6% 7% 35%	3828
April	1st to 10th	Night	8% 10% 3 8% 5% 4 4 4 4 6% 45%	2052
	11th to 20th	Night	9% 7% 3 7% 4 5% 4 3 4 6% 47%	1691
	21st to end	Night	9% 7% 2 5% 4 3 4 4 5% 6% 49%	1710
May	1st to 10th	Night	7% 7% 2 6% 5% 4 5% 4 6% 7% 46%	2860
	11th to 20th	Night	6% 6% 2 5% 3 3 3 3 5% 6% 59%	2834
	21st to end	Night	8% 5% 2 6% 4 4 4 3 6% 6% 52%	3110
June	1st to 10th	Night	6% 4 2 4 3 4 5% 4 6% 6% 55%	1535
	11th to 20th	Night	7% 5% 2 4 4 2 3 3 6% 7% 58%	1330
	21st to end	Night	3 3 1 3 2 3 3 3 4 5% 71%	1422
July	1st to 10th	Night	2 1 1 3 2 3 2 2 4 5% 74%	2540
	11th to 20th	Night	2 4 1 5% 4 4 4 3 5% 7% 62%	2690
	21st to end	Night	3 3 1 5% 3 3 4 3 4 6% 65%	3109
August	1st to 10th	Night	2 3 1 4 3 3 5% 4 5% 7% 62%	2847
	11th to 20th	Night	3 3 1 6% 4 4 4 3 4 5% 64%	2811
	21st to end	Night	4 3 1 3 2 2 3 2 4 4 72%	3146
September	1st to 10th	Night	3 2 1 4 3 3 3 3 4 5% 69%	2031
	11th to 20th	Night	6% 3 1 3 2 2 3 3 5% 5% 68%	2090
	21st to end	Night	6% 4 1 4 2 2 2 2 3 4 70%	2090
October	1st to 10th	Night	4 3 1 3 2 2 2 2 3 4 74%	3605
	11th to 20th	Night	8% 6% 2 5% 4 3 3 2 4 5% 58%	3778
	21st to end	Night	5% 6% 2 6% 4 3 5% 3 5% 7% 55%	4261
November	1st to 10th	Night	11% 8% 2 5% 5% 3 3 3 5% 7% 47%	2469
	11th to 20th	Night	8% 8% 3 5% 4 3 4 3 5% 7% 48%	2470
	21st to end	Night	7% 9% 2 6% 6% 4 4 4 5% 7% 46%	2600
December	1st to 10th	Night	10% 11% 4 10% 5% 4 4 3 5% 7% 36%	2660
	11th to 20th	Night	12% 12% 4 10% 5% 6% 5% 4 5% 8% 29%	3271
	21st to end	Night	9% 11% 5% 10% 7% 5% 5% 4 5% 6% 33%	4843

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% 8% 13% 15% 2 1	2539
	11th to 20th	Day	61% 9% 13% 13% 3 1	2794
	21st to end	Day	68% 9% 11% 8% 3 1	3146
February	1st to 10th	Day	53% 9% 14% 17% 6% 1	1710
	11th to 20th	Day	48% 8% 15% 20% 7% 2	1753
	21st to end	Day	49% 7% 15% 19% 9% 1	1570
March	1st to 10th	Day	45% 8% 12% 23% 11% 1	3284
	11th to 20th	Day	32% 6% 13% 33% 17%	3490
	21st to end	Day	49% 11% 17% 19% 4 1	3825
April	1st to 10th	Day	41% 7% 14% 23% 12% 3	2123
	11th to 20th	Day	37% 6% 11% 26% 18% 2	2440
	21st to end	Day	35% 6% 12% 27% 18% 1	2470
May	1st to 10th	Day	36% 5% 11% 25% 19% 5%	4110
	11th to 20th	Day	20% 4 12% 30% 24% 9%	4074
	21st to end	Day	29% 5% 12% 23% 29% 3	4477
June	1st to 10th	Day	25% 6% 11% 26% 27% 4	2631
	11th to 20th	Day	24% 4 11% 17% 27% 17%	2850
	21st to end	Day	14% 2 6% 13% 33% 31%	2749
July	1st to 10th	Day	10% 2 4 9% 14% 60%	4351
	11th to 20th	Day	17% 2 6% 8% 24% 43%	4195
	21st to end	Day	16% 3 5% 10% 29% 37%	4314
August	1st to 10th	Day	17% 2 6% 13% 30% 31%	4078
	11th to 20th	Day	16% 2 5% 14% 35% 27%	4067
	21st to end	Day	14% 2 4 14% 34% 32%	4520
September	1st to 10th	Day	18% 4 6% 15% 29% 28%	2143
	11th to 20th	Day	19% 4 7% 20% 29% 20%	2090
	21st to end	Day	19% 2 8% 22% 36% 12%	2090
October	1st to 10th	Day	20% 3 7% 17% 32% 21%	3370
	11th to 20th	Day	23% 4 8% 32% 26% 7%	3150
	21st to end	Day	26% 5% 15% 36% 18% 1	3296
November	1st to 10th	Day	41% 6% 15% 22% 14% 1	1710
	11th to 20th	Day	33% 7% 22% 28% 10% 1	1710
	21st to end	Day	43% 5% 18% 24% 11% 1	1558
December	1st to 10th	Day	52% 9% 14% 16% 8% 2	1520
	11th to 20th	Day	57% 11% 17% 13% 3	1924
	21st to end	Day	51% 7% 16% 16% 9% 1	2821
January	1st to 10th	Night	46% 10% 15% 24% 5% 1	4406
	11th to 20th	Night	54% 10% 15% 16% 4 1	4167
	21st to end	Night	60% 10% 15% 10% 5% 1	4521
February	1st to 10th	Night	50% 8% 16% 20% 6%	2470
	11th to 20th	Night	43% 7% 14% 22% 13% 2	2319
	21st to end	Night	45% 5% 13% 23% 11% 2	1884
March	1st to 10th	Night	44% 8% 13% 21% 14% 1	3589
	11th to 20th	Night	31% 6% 14% 30% 17% 1	3490
	21st to end	Night	44% 9% 15% 25% 6% 1	3828
April	1st to 10th	Night	39% 6% 13% 23% 13% 6%	2052
	11th to 20th	Night	37% 5% 11% 24% 20% 3	1691
	21st to end	Night	34% 5% 11% 25% 22% 3	1710
May	1st to 10th	Night	32% 5% 12% 22% 23% 6%	2860
	11th to 20th	Night	25% 3 8% 25% 29% 9%	2835
	21st to end	Night	30% 6% 9% 24% 29% 2	3110
June	1st to 10th	Night	26% 6% 12% 24% 27% 6%	1535
	11th to 20th	Night	26% 4 8% 16% 29% 16%	1330
	21st to end	Night	16% 3 4 13% 29% 35%	1422
July	1st to 10th	Night	13% 3 5% 7% 16% 56%	2500
	11th to 20th	Night	22% 2 5% 6% 22% 43%	2642
	21st to end	Night	19% 3 5% 7% 27% 39%	3011
August	1st to 10th	Night	20% 3 6% 11% 26% 34%	2838
	11th to 20th	Night	23% 3 6% 12% 27% 30%	2838
	21st to end	Night	17% 2 5% 9% 30% 37%	3146
September	1st to 10th	Night	18% 3 6% 14% 24% 36%	2031
	11th to 20th	Night	18% 4 7% 16% 31% 24%	2090
	21st to end	Night	20% 3 5% 18% 35% 19%	2090
October	1st to 10th	Night	16% 2 7% 14% 37% 24%	3605
	11th to 20th	Night	30% 2 5% 26% 27% 10%	3778
	21st to end	Night	29% 4 9% 34% 19% 4	4261
November	1st to 10th	Night	36% 5% 14% 24% 18% 3	2469
	11th to 20th	Night	34% 7% 15% 29% 14% 1	2470
	21st to end	Night	36% 6% 15% 30% 11% 2	2600
December	1st to 10th	Night	47% 7% 17% 19% 7% 3	2660
	11th to 20th	Night	53% 9% 15% 18% 5%	3272
	21st to end	Night	51% 6% 17% 15% 10%	4843

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	15% 7% 19% 29% 18% 12%	180
	11th to 20th	Day	16% 5% 20% 31% 19% 9%	252
	21st to end	Day	15% 5% 17% 33% 22% 7%	297
February	1st to 10th	Day	22% 9% 16% 33% 12% 7%	270
	11th to 20th	Day	16% 7% 22% 36% 14% 5%	349
	21st to end	Day	10% 6% 25% 38% 18% 2	382
March	1st to 10th	Day	14% 7% 17% 38% 21% 3	460
	11th to 20th	Day	10% 5% 17% 35% 26% 7%	460
	21st to end	Day	14% 8% 25% 34% 17% 2	506
April	1st to 10th	Day	16% 9% 22% 30% 20% 4	460
	11th to 20th	Day	9% 14% 27% 31% 13% 5%	452
	21st to end	Day	11% 14% 25% 26% 17% 7%	460
May	1st to 10th	Day	6% 14% 28% 27% 22% 3	463
	11th to 20th	Day	11% 7% 22% 28% 24% 7%	488
	21st to end	Day	8% 8% 19% 29% 25% 10%	529
June	1st to 10th	Day	6% 6% 19% 29% 29% 10%	623
	11th to 20th	Day	8% 6% 24% 32% 25% 5%	680
	21st to end	Day	3 4 24% 38% 23% 8%	579
July	1st to 10th	Day	2 5% 18% 35% 29% 10%	486
	11th to 20th	Day	5% 2 21% 35% 30% 8%	484
	21st to end	Day	4 1 13% 31% 37% 14%	531
August	1st to 10th	Day	7% 2 16% 32% 32% 11%	487
	11th to 20th	Day	4 4 14% 31% 33% 14%	477
	21st to end	Day	4 6% 13% 27% 32% 18%	539
September	1st to 10th	Day	3 4 14% 26% 33% 19%	490
	11th to 20th	Day	5% 4 15% 35% 28% 13%	490
	21st to end	Day	7% 4 18% 23% 36% 11%	490
October	1st to 10th	Day	9% 4 18% 29% 26% 14%	422
	11th to 20th	Day	7% 7% 21% 25% 24% 15%	300
	21st to end	Day	7% 11% 23% 35% 21% 3	330
November	1st to 10th	Day	15% 9% 20% 33% 16% 7%	282
	11th to 20th	Day	10% 8% 19% 40% 15% 9%	270
	21st to end	Day	14% 5% 19% 31% 24% 7%	270
December	1st to 10th	Day	15% 5% 21% 34% 18% 7%	270
	11th to 20th	Day	14% 5% 15% 40% 23% 3	270
	21st to end	Day	16% 9% 16% 35% 16% 7%	237
January	1st to 10th	Night	17% 4 15% 37% 23% 5%	760
	11th to 20th	Night	16% 4 16% 35% 24% 5%	760
	21st to end	Night	18% 4 15% 35% 23% 5%	836
February	1st to 10th	Night	18% 3 22% 38% 17% 2	760
	11th to 20th	Night	16% 3 19% 42% 19% 2	744
	21st to end	Night	11% 4 22% 41% 19% 2	628
March	1st to 10th	Night	15% 6% 16% 44% 16% 3	760
	11th to 20th	Night	10% 3 19% 42% 24% 3	760
	21st to end	Night	13% 6% 19% 42% 18% 2	836
April	1st to 10th	Night	12% 8% 19% 40% 19% 3	760
	11th to 20th	Night	11% 6% 22% 42% 15% 3	563
	21st to end	Night	11% 6% 22% 34% 23% 3	570
May	1st to 10th	Night	9% 6% 25% 39% 19% 2	570
	11th to 20th	Night	11% 5% 16% 36% 29% 4	561
	21st to end	Night	12% 6% 15% 33% 30% 5%	617
June	1st to 10th	Night	6% 7% 15% 38% 32% 3	537
	11th to 20th	Night	9% 6% 21% 39% 24% 1	380
	21st to end	Night	3 3 15% 44% 31% 4	380
July	1st to 10th	Night	2 2 15% 38% 39% 4	370
	11th to 20th	Night	4 2 16% 47% 30% 1	453
	21st to end	Night	3 1 10% 43% 39% 4	624
August	1st to 10th	Night	5% 1 10% 47% 34% 3	567
	11th to 20th	Night	4 2 13% 43% 36% 2	564
	21st to end	Night	6% 3 13% 37% 36% 5%	627
September	1st to 10th	Night	5% 2 11% 39% 36% 8%	731
	11th to 20th	Night	6% 2 12% 37% 34% 8%	760
	21st to end	Night	7% 3 14% 36% 31% 10%	760
October	1st to 10th	Night	9% 3 14% 38% 31% 5%	760
	11th to 20th	Night	10% 5% 12% 37% 31% 5%	760
	21st to end	Night	8% 4 19% 39% 26% 4	836
November	1st to 10th	Night	13% 5% 13% 39% 26% 4	760
	11th to 20th	Night	13% 2 17% 43% 20% 4	760
	21st to end	Night	9% 5% 18% 40% 24% 4	890
December	1st to 10th	Night	15% 5% 16% 42% 21% 1	950
	11th to 20th	Night	19% 4 18% 39% 18% 2	950
	21st to end	Night	20% 6% 20% 38% 14% 2	916

Page generated at 2024-11-03 00:11:08. Version ac07

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